feat(db): migration 153 — analyze_events shadow 컬럼

ALTER TABLE analyze_events ADD COLUMN IF NOT EXISTS 로 10개 shadow 컬럼:
subject_domain, risk_flags[], high_impact_task, escalated_to_26b,
escalation_reasons[], confidence, policy_violation, policy_violation_ids[],
shadow_would_route_to, policy_version.

+ 2 partial index:
- idx_analyze_events_shadow_ts (shadow_would_route_to IS NOT NULL)
- idx_analyze_events_policy_violation (policy_violation=true)

전부 nullable, 기본값 NULL. 아무도 쓰지 않음 — PR-B 의 DBShadowLogger 가
writer 추가 예정.

번호 153: 152 는 `feat(category): law` 가 점유 (e88640d).

BEGIN/COMMIT 없음 (CLAUDE.md: _run_migrations 단일 outer 트랜잭션).

answerability / new_facts_count 는 PR-B 의 migration 154+ 가 소유.

plan: ~/.claude/plans/wise-gliding-hippo.md

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

migrations/153_analyze_events_shadow.sql

@@ -0,0 +1,29 @@
+-- 153_analyze_events_shadow.sql
+-- AI Policy Layer (PR-A) — shadow 관측용 컬럼만 추가. 아무도 쓰지 않음.
+-- PR-B 가 DBShadowLogger 구현 후 writer 추가 예정.
+--
+-- plan: ~/.claude/plans/wise-gliding-hippo.md
+-- axis 원칙: feedback_category_vs_ai_domain_axis.md (subject_domain 은 정책 축,
+--            documents.category 매칭 키로 쓰지 않음)
+--
+-- 주의: _run_migrations 는 단일 outer 트랜잭션으로 실행됨 — BEGIN/COMMIT 금지.
+
+ALTER TABLE analyze_events
+    ADD COLUMN IF NOT EXISTS subject_domain        TEXT,
+    ADD COLUMN IF NOT EXISTS risk_flags            TEXT[],
+    ADD COLUMN IF NOT EXISTS high_impact_task      BOOLEAN,
+    ADD COLUMN IF NOT EXISTS escalated_to_26b      BOOLEAN,
+    ADD COLUMN IF NOT EXISTS escalation_reasons    TEXT[],
+    ADD COLUMN IF NOT EXISTS confidence            REAL,
+    ADD COLUMN IF NOT EXISTS policy_violation      BOOLEAN,
+    ADD COLUMN IF NOT EXISTS policy_violation_ids  TEXT[],
+    ADD COLUMN IF NOT EXISTS shadow_would_route_to TEXT,
+    ADD COLUMN IF NOT EXISTS policy_version        TEXT;
+
+CREATE INDEX IF NOT EXISTS idx_analyze_events_shadow_ts
+    ON analyze_events (created_at)
+    WHERE shadow_would_route_to IS NOT NULL;
+
+CREATE INDEX IF NOT EXISTS idx_analyze_events_policy_violation
+    ON analyze_events (created_at)
+    WHERE policy_violation = true;