feat(guardrails): high-priority guardrail hooks — CI hard block + architecture enforcement

[terisuke]

Summary

Implement high-priority guardrail hooks missing from guardrail.ts (currently ~30% CC hook coverage).

Hooks to Implement

High Priority

• CI hard block (block-merge-without-ci): Block gh pr merge unless gh pr checks shows all green. Currently only review-gate exists.
• Architecture layer enforcement (enforce-architecture-layers): Warn/block cross-layer imports (e.g., UI importing directly from DB layer)
• Domain naming convention (enforce-domain-naming): Advisory for naming violations in domain entities

Medium Priority

• Post-deploy verify (post-deploy-verify): After git push, remind to verify deployment
• Memory update on commit (enforce-memory-update-on-commit): Advisory to update AGENTS.md/docs after significant commits

Low Priority

• Post-merge issue close (post-merge-close-issues): Auto-suggest closing related issues after merge

Implementation Approach

All hooks go into packages/guardrails/profile/plugins/guardrail.ts as additional checks in existing hook points (tool.execute.before, tool.execute.after).

Ref

Master Plan #51, Gap analysis report