fix: #412/#413/#414 runtime stability and PR governance preflight

## #413 — runtime_verify_monitor.sh pipefail fix
- find_live_pids() now captures pgrep output via local variable with || true
  so pipefail never triggers on no-match (pgrep exit 1)
- Regression test added: monitor survives MAX_LOOPS=1 without crash

## #412 — startup crash logging improvement
- Add asyncio.CancelledError catch in sync_positions_from_broker call
  so BaseException-level cancellations are logged before propagating
- Provides evidence in run log if CancelledError causes future startup aborts

## #414 — PR governance preflight
- validate_pr_body.py: add REQ-ID/TASK-ID/TEST-ID pattern checks (--no-governance flag to skip)
- docs/workflow.md: new "PR Governance Preflight (Mandatory)" section
- docs/commands.md: "PR Body Governance Preflight" section before tea pulls create
- Tests: 4 new governance traceability tests in test_validate_pr_body.py

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

workflow/session-handover.md

@@ -145,3 +145,11 @@
 - next_ticket: #409
 - process_gate_checked: process_ticket=#306,#308 merged_to_feature_branch=yes
 - risks_or_notes: #409 코드수정/검증 후 프로그램 재시작 및 24h 런타임 모니터링 수행, 모니터 이상 징후는 별도 이슈 발행
+
+### 2026-03-04 | session=claude-issues412-413-414
+- branch: feature/issue-412-413-414-runtime-and-governance
+- docs_checked: docs/workflow.md, docs/commands.md, docs/agent-constraints.md
+- open_issues_reviewed: #412, #413, #414
+- next_ticket: #412, #413, #414
+- process_gate_checked: process_ticket=#306,#308 merged_to_feature_branch=yes
+- risks_or_notes: #413 pipefail fix (find_live_pids), #412 startup crash 로깅 강화, #414 PR 거버넌스 preflight 추가