feat(estimation): add estimation actor YAML template and role-aware registration validation

- Add `role_hint` and `response_format` support to actor schema.
- Add non-fatal estimation-role compatibility warnings in actor registration CLI flows.
- Add preflight warning path when `estimation` actor is missing `response_format`.
- Add `examples/actors/estimator.yaml` and update actor examples documentation/tests.
- Update integration helper expectations (m1/m2/m3/m6) for missing provider config in local test env.

ISSUES CLOSED: #650

examples/actors/estimator.yaml

@@ -0,0 +1,62 @@
+# Estimation Actor Example
+# Produces structured cost/risk/duration estimates prior to execution.
+
+name: local/estimator
+type: llm
+description: Estimates implementation effort, risk, and timeline before execution
+version: "1.0"
+
+model: gpt-4
+role_hint: estimation
+context_view: strategist
+
+system_prompt: |
+  You are an estimation specialist.
+  Assess the requested work and produce:
+  - Effort estimate (hours and confidence)
+  - Duration estimate (best/likely/worst case)
+  - Risk assessment with severity and mitigation suggestions
+  - Key assumptions and unknowns
+
+  Always return valid JSON matching the provided response_format schema.
+
+response_format:
+  $schema: "https://json-schema.org/draft/2020-12/schema"
+  title: EstimationReport
+  type: object
+  required:
+    - cost_hours
+    - duration_days
+    - risk_level
+    - confidence
+    - assumptions
+  properties:
+    cost_hours:
+      type: number
+      minimum: 0
+    duration_days:
+      type: number
+      minimum: 0
+    risk_level:
+      type: string
+      enum: [low, medium, high]
+    confidence:
+      type: number
+      minimum: 0
+      maximum: 1
+    assumptions:
+      type: array
+      items:
+        type: string
+    mitigation_suggestions:
+      type: array
+      items:
+        type: string
+  additionalProperties: false
+
+tools:
+  - files/read_file
+  - files/list_directory
+
+skills:
+  - local/file-ops