Title#

Harden PhaseRouterService and PhaseHooksService idempotency for BullMQ retry

Problem#

BullMQ stalled-job retries could produce duplicate side effects — duplicate task rows, duplicate GitHub comments, and double Claude invocations — breaking the pipeline for issues with AW-13 (BullMQ migration).

Task / Link#

Closes #458

Changes#

• TaskStateService.createTask() wrapped with try/catch to fall back to existing task on unique-constraint race
• PhaseHooksService.onPhaseBlocked(): idempotency guard using eventService.countByType to skip duplicate blocked comments
• PhaseHooksService.onCompoundComplete(): idempotency guard to skip duplicate completion comments
• PhaseRouterService.executePhase(): defensive re-entry guard (belt-and-suspenders) if phase status is already active
• BullMQ stall-retry guard: skips phase_* re-execution when phase is failed and task is gated
• Added BullMQ retry idempotency test suites to both phase-router.service.spec.ts and phase-hooks.service.spec.ts

Notes#

• Concurrent multi-worker calls for the same job remain out of scope (per issue)
• getOrCreateWorktree() was confirmed already idempotent
• Comment dedup uses task-state event flags rather than GitHub API calls to avoid rate-limit pressure

Testing#

• 826 unit tests passing (npm run test)
• Lint clean (npm run lint)