Execution + rollback + result emission

[CodeBuildder]

Context

Executes the heal plan step by step; rolls back on failure; emits outcome for calibration. Parent: #38.

Acceptance Criteria

• Each heal step invokes the corresponding MCP tool and checks for success
• On step failure, rollback steps execute in reverse order
• Final outcome (success|failure|partial) emitted as an action event to the bus
• Outcome feeds calibration recorder with predicted_outcome vs actual_outcome

Dependencies

Blocked by: none | Blocks: none

Notes

No model tier.