feat(server): add Kubernetes Helm chart for server deployment (#1085)

## Summary

This PR adds Kubernetes Helm deployment support for the CleverAgents server.

Closes #928

### What this PR includes

- Helm chart under `k8s/` with Deployment, Service, optional Ingress, ConfigMap,
  ServiceAccount, Secrets, NOTES, and optional Redis subchart configuration.
- Multi-stage `Dockerfile.server` for server runtime deployment.
- Deployment-focused docs in `k8s/README.md`.
- Behave + Robot + benchmark coverage for chart/deployment wiring.

### Review fixes applied (cycle 11 — hurui200320 review #2687)

**Critical fix:**

1. **CI SHA256 checksum verification fixed** — All 3 Helm install blocks (`unit_tests`, `integration_tests`, `helm` jobs) now save the tarball using its original filename (`helm-v3.16.4-linux-amd64.tar.gz`) instead of `helm.tgz`, so the `.sha256sum` file can correctly locate and verify it. This was causing all 3 CI Helm jobs to fail with "No such file or directory".

**Major fixes (test coverage gaps):**

2. **405 Allow header now tested** — The existing "POST to known path returns method not allowed" scenario now asserts that the `Allow: GET` header is present. Added a second 405 scenario testing `POST /live` for broader `_KNOWN_PATHS` coverage (review item #11).
3. **Security-hardening headers now tested** — New scenario "HTTP responses include security-hardening headers" verifies `content-length`, `x-content-type-options: nosniff`, and `cache-control: no-store` headers are present on HTTP responses.
4. **Lifespan warning logging now tested** — New scenario "Unrecognised lifespan message type logs warning and continues" queues `lifespan.startup` → `lifespan.bogus` → `lifespan.shutdown` and verifies: (a) the app completes the lifespan cycle cleanly, (b) a warning is logged mentioning the unrecognised type.

### Review fixes applied (cycle 10)

**Critical/Major fixes (from hurui200320's prior REQUEST_CHANGES):**

1. **Rebased branch onto master** — Removed merge commit per CONTRIBUTING.md rebase-only policy. Clean linear history restored.
2. **Fixed commit message body** — Replaced literal `\n` sequences with actual newlines. `ISSUES CLOSED: #928` footer is now on its own line after a blank separator.
3. **Moved uvicorn import to module top level** — `from uvicorn import run as uvicorn_run` is now at the top of `src/cleveragents/cli/commands/server.py` per Import Guidelines. Updated test mock target from `uvicorn.run` to `cleveragents.cli.commands.server.uvicorn_run`.
4. **Added SHA256 checksum verification** — All three Helm CLI install blocks in `.forgejo/workflows/ci.yml` now download and verify `helm.sha256sum` before extracting the binary.

**Minor fixes:**

5. **Added `Dockerfile.server` build to CI** — New "Build Docker image (Server)" step in the `docker` job validates the server Dockerfile.
6. **ASGI 405 Method Not Allowed** — Known paths (`/`, `/live`, `/ready`, `/health`) now return 405 with `Allow: GET` header for non-GET methods, per RFC 9110 §15.5.6. Added `_KNOWN_PATHS` frozenset.
7. **WebSocket close protocol fix** — App now calls `await receive()` to consume the `websocket.connect` event before closing. Changed close code from 1000 (Normal Closure) to 1008 (Policy Violation).
8. **Lifespan handler logging** — Unrecognised lifespan message types are now logged as warnings instead of silently consumed.
9. **Security-hardening headers** — `_send_response` now includes `content-length`, `x-content-type-options: nosniff`, and `cache-control: no-store` on all HTTP responses.
10. **`.dockerignore` credential patterns** — Added `*.pem`, `*.key`, `*.p12`, `*.pfx`, `credentials*.json`.
11. **`--log-level` validation** — Constrained to `click.Choice(["critical", "error", "warning", "info", "debug", "trace"])` for clean CLI validation errors.
12. **Reverted unrelated semgrep pre-commit change** — `pass_filenames` and `entry` restored to original values per atomic commit hygiene.
13. **Removed unused `ReceiveCallable` type alias** and `Callable`/`Awaitable` imports from `asgi_app_steps.py`.
14. **Fixed redundant `shutil.which("helm")` check** — `_skip_if_helm_missing` now returns `bool` to eliminate the duplicate check in `_render_chart`.
15. **Improved test deque error handling** — Lifespan test receive mock now raises descriptive `AssertionError` instead of opaque `IndexError`.
16. **Scope type dispatch** — Changed `if/if/if` to `if/elif/elif` for mutually exclusive ASGI scope types.
17. **Dockerfile.server base image** — Standardised to `python:3.13-slim` (floating minor) consistent with CLI Dockerfile.
18. **Dockerfile layer caching** — Split `uv pip install build` and `python -m build` into separate `RUN` instructions.
19. **Removed extraneous double blank line** in Dockerfile.server.

### Deferred items (acknowledged, not in scope)

- PodDisruptionBudget, HorizontalPodAutoscaler, NetworkPolicy — Follow-up for production hardening.
- `appVersion: "1.0.0"` placeholder — Needs tracking issue for release versioning alignment.
- Readiness probe with downstream dependency checks — Documented limitation.
- Cross-system test for probe paths matching ASGI routes — Test enhancement.
- Improved benchmarks (helm template timing vs PyYAML parsing) — Benchmark quality improvement.
- CI DRY violation (Helm install 3×) — Code quality improvement, consider composite action.
- File length limits exceeded (`k8s_helm_chart_steps.py` 551 lines, `helper_k8s_helm_chart.py` 678 lines) — Non-blocking, can be split in follow-up.
- `runAsGroup: 1000` in pod security context — Defense-in-depth improvement.
- HEAD method support on known paths — RFC compliance, does not affect K8s probes.
- `click.Choice` log-level validation via CLI runner test — Test gap.

### Scope note: status-check CI gate

The `status-check` job now includes `integration_tests`, `e2e_tests`, and `helm` in its `needs` list. The `helm` job is new in this PR. The `integration_tests` and `e2e_tests` additions fix previously-missing gate checks — included here since this PR modifies both of those jobs to install Helm.

### Quality gates

- `nox -e lint` ✅
- `nox -e typecheck` ✅
- `nox -e unit_tests` ✅ (12,321 scenarios passed, 4 skipped)
- `nox -e integration_tests` — 3 pre-existing failures in unrelated areas (plan correction, resource types)
- `nox -e e2e_tests` — pre-existing failures (LLM API keys not available in local env)
- `nox -e coverage_report` ✅ (**97.7%**)

Reviewed-on: #1085
Reviewed-by: Jeffrey Phillips Freeman <jeffrey.freeman@cleverthis.com>
Co-authored-by: Brent E. Edwards <brent.edwards@cleverthis.com>
Co-committed-by: Brent E. Edwards <brent.edwards@cleverthis.com>

k8s/templates/NOTES.txt

@@ -0,0 +1,34 @@
+CleverAgents Server has been deployed!
+
+{{- if .Values.ingress.enabled }}
+
+The server is accessible via Ingress:
+{{- range $host := .Values.ingress.hosts }}
+  {{- range .paths }}
+  http{{ if $.Values.ingress.tls }}s{{ end }}://{{ $host.host }}{{ .path }}
+  {{- end }}
+{{- end }}
+
+{{- if .Values.ingress.tls }}
+TLS termination is configured at the Ingress controller.
+{{- else }}
+⚠️  Insecure ingress mode is enabled (`ingress.allowInsecure=true`).
+This mode is for local/dev use only and is not suitable for production.
+{{- end }}
+
+{{- else }}
+
+To access the server, use port-forward:
+
+  kubectl port-forward svc/{{ include "cleveragents.fullname" . }} {{ .Values.service.port }}:{{ .Values.service.port }}
+
+Then access: http://localhost:{{ .Values.service.port }}
+
+{{- end }}
+
+{{- if .Values.redis.enabled }}
+
+Redis is enabled for session affinity and rate limiting.
+{{- end }}
+
+For more information, see the deployment README in k8s/README.md.

k8s/templates/_helpers.tpl

@@ -0,0 +1,72 @@
+{{/*
+Expand the name of the chart.
+*/}}
+{{- define "cleveragents.name" -}}
+{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
+{{- end }}
+
+{{/*
+Create a default fully qualified app name.
+We truncate at 63 chars because some Kubernetes name fields are limited
+to this (by the DNS naming spec). If release name contains chart name
+it will be used as a full name.
+*/}}
+{{- define "cleveragents.fullname" -}}
+{{- if .Values.fullnameOverride }}
+{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
+{{- else }}
+{{- $name := default .Chart.Name .Values.nameOverride }}
+{{- if contains $name .Release.Name }}
+{{- .Release.Name | trunc 63 | trimSuffix "-" }}
+{{- else }}
+{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
+{{- end }}
+{{- end }}
+{{- end }}
+
+{{/*
+Create chart name and version as used by the chart label.
+*/}}
+{{- define "cleveragents.chart" -}}
+{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" }}
+{{- end }}
+
+{{/*
+Common labels.
+*/}}
+{{- define "cleveragents.labels" -}}
+helm.sh/chart: {{ include "cleveragents.chart" . }}
+{{ include "cleveragents.selectorLabels" . }}
+{{- if .Chart.AppVersion }}
+app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
+{{- end }}
+app.kubernetes.io/managed-by: {{ .Release.Service }}
+{{- end }}
+
+{{/*
+Selector labels.
+*/}}
+{{- define "cleveragents.selectorLabels" -}}
+app.kubernetes.io/name: {{ include "cleveragents.name" . }}
+app.kubernetes.io/instance: {{ .Release.Name }}
+{{- end }}
+
+{{/*
+Create the name of the service account to use.
+*/}}
+{{- define "cleveragents.serviceAccountName" -}}
+{{- if .Values.serviceAccount.create }}
+{{- default (include "cleveragents.fullname" .) .Values.serviceAccount.name }}
+{{- else }}
+{{- default "default" .Values.serviceAccount.name }}
+{{- end }}
+{{- end }}
+
+{{/*
+Redis host helper - returns the Redis service hostname.
+*/}}
+{{- define "cleveragents.redisHost" -}}
+{{- if .Values.redis.enabled }}
+{{- printf "%s-redis-master" .Release.Name }}
+{{- end }}
+{{- end }}

k8s/templates/configmap.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: {{ include "cleveragents.fullname" . }}-config
+  labels:
+    {{- include "cleveragents.labels" . | nindent 4 }}
+data:
+  # NOTE: The Deployment template overrides these values via CLI args
+  # (command/args in deployment.yaml).  Uvicorn CLI args take precedence
+  # over environment variables.  These ConfigMap entries serve as a
+  # fallback for any code paths that read env vars directly (e.g.,
+  # Settings model defaults) rather than relying on CLI args.
+  CLEVERAGENTS_SERVER_HOST: {{ .Values.server.host | quote }}
+  CLEVERAGENTS_SERVER_PORT: {{ .Values.server.port | quote }}
+  CLEVERAGENTS_LOG_LEVEL: {{ .Values.server.logLevel | quote }}

k8s/templates/deployment.yaml

@@ -0,0 +1,137 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: {{ include "cleveragents.fullname" . }}
+  labels:
+    {{- include "cleveragents.labels" . | nindent 4 }}
+spec:
+  replicas: {{ .Values.replicaCount }}
+  selector:
+    matchLabels:
+      {{- include "cleveragents.selectorLabels" . | nindent 6 }}
+  template:
+    metadata:
+      {{- with .Values.podAnnotations }}
+      annotations:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
+      labels:
+        {{- include "cleveragents.selectorLabels" . | nindent 8 }}
+    spec:
+      automountServiceAccountToken: false
+      {{- with .Values.imagePullSecrets }}
+      imagePullSecrets:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
+      serviceAccountName: {{ include "cleveragents.serviceAccountName" . }}
+      securityContext:
+        {{- toYaml .Values.podSecurityContext | nindent 8 }}
+      containers:
+        - name: {{ .Chart.Name }}
+          securityContext:
+            {{- toYaml .Values.securityContext | nindent 12 }}
+          image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
+          imagePullPolicy: {{ .Values.image.pullPolicy }}
+          command: ["python", "-m", "cleveragents"]
+          args:
+            - "server"
+            - "serve"
+            - "--app"
+            - "cleveragents.a2a.asgi:app"
+            - "--host"
+            - {{ .Values.server.host | quote }}
+            - "--port"
+            - {{ .Values.server.port | quote }}
+            - "--workers"
+            - {{ .Values.server.workers | quote }}
+            - "--log-level"
+            - {{ .Values.server.logLevel | quote }}
+          ports:
+            - name: http
+              containerPort: {{ .Values.server.port }}
+              protocol: TCP
+          envFrom:
+            - configMapRef:
+                name: {{ include "cleveragents.fullname" . }}-config
+          env:
+            {{- if .Values.database.existingSecret }}
+            - name: CLEVERAGENTS_DATABASE_URL
+              valueFrom:
+                secretKeyRef:
+                  name: {{ .Values.database.existingSecret }}
+                  key: {{ .Values.database.existingSecretKey }}
+            {{- else if .Values.database.url }}
+            - name: CLEVERAGENTS_DATABASE_URL
+              valueFrom:
+                secretKeyRef:
+                  name: {{ include "cleveragents.fullname" . }}-db
+                  key: database-url
+            {{- else }}
+            {{- fail "database configuration is required: set database.existingSecret or database.url" }}
+            {{- end }}
+            {{- if .Values.redis.enabled }}
+            - name: CLEVERAGENTS_REDIS_HOST
+              value: {{ include "cleveragents.redisHost" . }}
+            - name: CLEVERAGENTS_REDIS_PORT
+              value: "6379"
+            {{- if .Values.redis.auth.enabled }}
+            {{- if .Values.redis.auth.existingSecret }}
+            - name: CLEVERAGENTS_REDIS_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: {{ .Values.redis.auth.existingSecret }}
+                  key: {{ .Values.redis.auth.existingSecretPasswordKey }}
+            {{- else if .Values.redis.auth.password }}
+            - name: CLEVERAGENTS_REDIS_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: {{ include "cleveragents.fullname" . }}-redis
+                  key: redis-password
+            {{- else }}
+            - name: CLEVERAGENTS_REDIS_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: {{ .Release.Name }}-redis
+                  key: redis-password
+            {{- end }}
+            {{- end }}
+            {{- end }}
+            {{- with .Values.extraEnv }}
+            {{- toYaml . | nindent 12 }}
+            {{- end }}
+          livenessProbe:
+            {{- toYaml .Values.livenessProbe | nindent 12 }}
+          readinessProbe:
+            {{- toYaml .Values.readinessProbe | nindent 12 }}
+          resources:
+            {{- toYaml .Values.resources | nindent 12 }}
+          volumeMounts:
+            - name: tmp
+              mountPath: /tmp
+            - name: app-data
+              mountPath: /app/data
+            {{- with .Values.extraVolumeMounts }}
+            {{- toYaml . | nindent 12 }}
+            {{- end }}
+      volumes:
+        - name: tmp
+          emptyDir:
+            sizeLimit: 100Mi
+        - name: app-data
+          emptyDir:
+            sizeLimit: 1Gi
+        {{- with .Values.extraVolumes }}
+        {{- toYaml . | nindent 8 }}
+        {{- end }}
+      {{- with .Values.nodeSelector }}
+      nodeSelector:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
+      {{- with .Values.affinity }}
+      affinity:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
+      {{- with .Values.tolerations }}
+      tolerations:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}

k8s/templates/ingress.yaml

@@ -0,0 +1,53 @@
+{{- if .Values.ingress.enabled -}}
+{{- if and (not .Values.ingress.allowInsecure) (not .Values.ingress.tls) -}}
+{{- fail "ingress.tls is required when ingress.enabled=true (set ingress.allowInsecure=true only for local/dev)" -}}
+{{- end }}
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: {{ include "cleveragents.fullname" . }}
+  labels:
+    {{- include "cleveragents.labels" . | nindent 4 }}
+  {{- if or .Values.ingress.tls .Values.ingress.annotations }}
+  annotations:
+    {{- if and .Values.ingress.tls (not (hasKey (default dict .Values.ingress.annotations) "nginx.ingress.kubernetes.io/ssl-redirect")) }}
+    # NOTE: This annotation is specific to the NGINX Ingress Controller.
+    # If using a different controller (e.g., Traefik, HAProxy), adjust
+    # or remove this annotation accordingly.  Omitted when the user
+    # explicitly sets the annotation in ingress.annotations.
+    nginx.ingress.kubernetes.io/ssl-redirect: "true"
+    {{- end }}
+    {{- with .Values.ingress.annotations }}
+    {{- toYaml . | nindent 4 }}
+    {{- end }}
+  {{- end }}
+spec:
+  {{- if .Values.ingress.className }}
+  ingressClassName: {{ .Values.ingress.className }}
+  {{- end }}
+  {{- if .Values.ingress.tls }}
+  tls:
+    {{- range .Values.ingress.tls }}
+    - secretName: {{ .secretName }}
+      hosts:
+        {{- range .hosts }}
+        - {{ . | quote }}
+        {{- end }}
+    {{- end }}
+  {{- end }}
+  rules:
+    {{- range .Values.ingress.hosts }}
+    - host: {{ .host | quote }}
+      http:
+        paths:
+          {{- range .paths }}
+          - path: {{ .path }}
+            pathType: {{ .pathType }}
+            backend:
+              service:
+                name: {{ include "cleveragents.fullname" $ }}
+                port:
+                  name: http
+          {{- end }}
+    {{- end }}
+{{- end }}

k8s/templates/secrets.yaml

@@ -0,0 +1,23 @@
+{{- if and .Values.database.url (not .Values.database.existingSecret) }}
+apiVersion: v1
+kind: Secret
+metadata:
+  name: {{ include "cleveragents.fullname" . }}-db
+  labels:
+    {{- include "cleveragents.labels" . | nindent 4 }}
+type: Opaque
+stringData:
+  database-url: {{ .Values.database.url | quote }}
+{{- end }}
+{{- if and .Values.redis.enabled .Values.redis.auth.enabled .Values.redis.auth.password (not .Values.redis.auth.existingSecret) }}
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: {{ include "cleveragents.fullname" . }}-redis
+  labels:
+    {{- include "cleveragents.labels" . | nindent 4 }}
+type: Opaque
+stringData:
+  redis-password: {{ .Values.redis.auth.password | quote }}
+{{- end }}

k8s/templates/service.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: {{ include "cleveragents.fullname" . }}
+  labels:
+    {{- include "cleveragents.labels" . | nindent 4 }}
+spec:
+  type: {{ .Values.service.type }}
+  ports:
+    - port: {{ .Values.service.port }}
+      targetPort: http
+      protocol: TCP
+      name: http
+  selector:
+    {{- include "cleveragents.selectorLabels" . | nindent 4 }}

k8s/templates/serviceaccount.yaml

@@ -0,0 +1,13 @@
+{{- if .Values.serviceAccount.create -}}
+apiVersion: v1
+kind: ServiceAccount
+automountServiceAccountToken: false
+metadata:
+  name: {{ include "cleveragents.serviceAccountName" . }}
+  labels:
+    {{- include "cleveragents.labels" . | nindent 4 }}
+  {{- with .Values.serviceAccount.annotations }}
+  annotations:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
+{{- end }}