feat: add AI writing chat workspace

offline-backend-20260512/backend/CLAUDE.md

@@ -264,6 +264,10 @@ FastAPI application on port 8001 with health check at `GET /health`. Set `GATEWA
 
 Proxied through nginx: `/api/langgraph/*` ? LangGraph, all other `/api/*` ? Gateway.
 
+### AI Writing Intent Router (对话驱动写作台意图路由)
+
+Backs the frontend「AI 写作·对话版」page's unified bottom composer. `POST /api/ai-writing/sessions/{session_id}/intent` (owner-checked; in `routers/ai_writing.py`) reads the session's graph checkpoint via the shared `app.state.checkpointer` — the **pending interrupt is the authoritative pause point** (the frontend's claimed `pause_point` is only a fallback when the checkpoint can't be read) — then routes the user's free text through `deerflow/agents/ai_writing/intent_router.py::parse_user_intent`: an LLM call (session's `model_name` + `fallback_chain` model fault-tolerance) that returns `{intent, pause_point, action, payload, need_research, research_query, answer, confidence, clarify}`. Safety boundaries in `normalize_intent_result`: **per-pause action whitelist strictly aligned to graph.py's real resume actions** (`ALLOWED_ACTIONS`), no pause → no action, high-cost actions (`finalize` / `force_finalize` / query-less覆盖式 `re_search`) require confidence ≥ 0.85 else downgrade to `clarify`, payload key-whitelist cleaning (material-id filtering, review-issue index bounds, section-decision back-fill with the majority decision). QA intents return `answer` directly from the context snapshot (`build_context_snapshot` — stage-tailored: materials with ids / outline / draft body capped / review issues with indices). Model failures never 5xx — they degrade to clarify. Prompts in `agents/ai_writing/prompts/intent_router_prompts.py`; tests `tests/test_ai_writing_intent.py`.
+
 ### AI Writing Built-in Functional Agents (????????)
 
 The AI-writing graph (`packages/harness/deerflow/agents/ai_writing/`) has four stage "brains" ? ?????? / ????? / ?? / ?? ? that can each run in one of two modes, switched per-stage by `config.yaml ? ai_writing.use_builtin_agents.{researcher,outliner,writer,editor}` (default **false**, mtime hot-reloaded, new sessions pick up changes immediately):