fix(actor,preflight,tests): resolve PR #975 review findings and stabilize full-suite coverage runs

Address review-driven fixes across actor schema, preflight guardrails, docs/examples,
and Behave/Robot coverage: unify preflight warning behavior with shared role-warning logic,
resolve actor-name to config payloads in production preflight flow, harden response_format
validation/coercion edge cases, extract duplicated helper logic, and expand negative-path
test coverage. Also fix cross-scenario patcher leakage in step modules to eliminate
full-run-only coverage failures.

examples/actors/estimator.yaml

@@ -3,7 +3,7 @@
 
 name: local/estimator
 type: llm
-description: Estimates implementation effort, risk, and timeline before execution
+description: Generates pre-execution effort, duration, and risk estimates for implementation planning
 version: "1.0"
 
 model: gpt-4
@@ -18,10 +18,10 @@ system_prompt: |
   - Risk assessment with severity and mitigation suggestions
   - Key assumptions and unknowns
 
-  Always return valid JSON matching the provided response_format schema.
+  Return JSON-shaped output suitable for machine parsing.
 
 response_format:
-  $schema: "https://json-schema.org/draft/2020-12/schema"
+  "$schema": "https://json-schema.org/draft/2020-12/schema"
   title: EstimationReport
   type: object
   required: