feat(#58): L3 dormant trigger guard -- DORMANT-TRIGGERS.yaml + checker + orchestrator hook

P5-1 docs/architecture/DORMANT-TRIGGERS.yaml -- 5 entries (IMP-16/17/18/19 active + IMP-20 followup-linked #55).
P5-2 scripts/check_dormant_triggers.py -- standalone, reads registry, scans tree + diff, writes .orchestrator/dormant_alerts.json, exit 0 always.
P5-3 orchestrator.py -- _check_dormant_triggers() helper + Stage 4->5 informational alert branch (skips audit-only, never blocks).
P5-4 tests/orchestrator_unit/test_dormant_triggers.py -- 30 cases (yaml schema, registry contents, checker matching, false-positive guards, manual-evidence skip, orchestrator branch, audit bypass, governance ref).
P5-5 PROJECT-INTENT-AND-GOVERNANCE.md -- single anti-patterns row referencing the L3 registry as binding contract surface.

Tests: pytest -q tests = 337 passed (baseline 307 + 30 new).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/architecture/PROJECT-INTENT-AND-GOVERNANCE.md

@@ -157,6 +157,7 @@ Q~Y 검토 결과를 22-step 의 어느 step 에 어떤 부품을 가져올지
 | "이슈 본문은 참고일뿐" | 본문의 (관련 step, source, scope, guardrails) 가 binding anchor |
 | "Phase R / R' / Q 의 path 로 돌아가도 됨" | 회귀 금지선 4 항목 (INSIGHT-MAP §0) 절대 위반 X |
 | "destination 외 추가 기능도 욕심내자" | 22-step + AI frame generation 까지가 목표. 그 이상은 별도 결정 |
+| "문서에 박힌 dormant 항목은 자동 실행 안 됨" | L3 registry [`DORMANT-TRIGGERS.yaml`](DORMANT-TRIGGERS.yaml) + `scripts/check_dormant_triggers.py` 가 orchestrator Stage 4→5 transition 에서 informational alert 로 발화 (closed 이슈 #16/#17/#18/#19/#20 의 trigger-on-X contract) |
 
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