feat(ingest): devonagent 트랙 Phase 1 ingest 활성화

DEVONagent/DEVONthink 가 발견한 웹페이지를 NAS Web/ drop → file_watcher
ingest → extract 4-tier fallback (trafilatura/sibling-md/readability/bs4)
→ embed + chunk 까지. classify/preview/markdown SKIP.

- source_channel='devonagent' (migration 001 dormant 활성화)
- file_watcher: SCAN_TARGETS 통합 + Web/ rglob + canonical_url dedup +
  sidecar 누락 정책 (skip 안 함, web_meta.sidecar_missing=true flag)
- extract_worker: HTML+devonagent 분기 + md_extraction_engine 4-tier 구분
  (trafilatura → sibling .md ≥200char → readability+markdownify → bs4_text)
- queue_consumer: enqueue_next_stage 의 extract stage 만 source_channel-
  aware override (devonagent → [embed, chunk])
- classify_worker: devonagent safety skip (law_monitor 패턴 mirror,
  ai_domain='Web', ai_tags=['Web/{host}'])
- requirements: trafilatura/readability-lxml/markdownify 추가
- docs: devonthink-web-bridge.md 설치 가이드 + first-wins 정책 명시

Phase 1 closure 기준 = 재료 품질 (검색 가능 + 노이즈율 + dedup + 엔진 분포).
활용처(ai_tldr/digest/PKM 회고)는 1-2주 OR 30-50건 관찰 후 별 PR 에서 결정.

Plan: ~/.claude/plans/db-snuggly-petal.md

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

app/workers/queue_consumer.py

@@ -103,13 +103,36 @@ async def enqueue_next_stage(document_id: int, current_stage: str):
     §3 추가:
       stt → [classify]  (audio 는 extract 건너뛰고 stt 가 extracted_text 를 채움)
       thumbnail → [] (video 는 leaf — classify/embed 없음)
+
+    Web/Blog ingest (devonagent 트랙) — plan db-snuggly-petal.md:
+      source_channel='devonagent' 인 doc 의 extract 완료 시
+      classify/preview/markdown 전부 SKIP → [embed, chunk] 만 enqueue.
+      AI 가공 (ai_tldr/ai_bullets 등) 은 별 PR (Mac mini derived-worker).
     """
+    # source_channel-aware override (extract stage 만). source_channel 누락 시 _default.
+    extract_override_by_channel = {
+        "devonagent": ["embed", "chunk"],
+    }
+
     next_stages = {
         "extract": ["classify", "preview"],
         "classify": ["embed", "chunk", "markdown"],
         "stt": ["classify"],
     }
-    stages = next_stages.get(current_stage, [])
+
+    # extract 의 경우만 doc.source_channel 을 lookup 해서 override 적용
+    if current_stage == "extract":
+        from models.document import Document
+        async with async_session() as lookup_session:
+            doc = await lookup_session.get(Document, document_id)
+            sc = doc.source_channel if doc else None
+        if sc in extract_override_by_channel:
+            stages = extract_override_by_channel[sc]
+        else:
+            stages = next_stages.get(current_stage, [])
+    else:
+        stages = next_stages.get(current_stage, [])
+
     if not stages:
         return