feat(ai写作): 草稿局部修改只改命中章节，支持改章节标题，修改时右侧流式重写

用户在草稿确认填修改意见(user_revise)时，按章节定位只重写命中章节、
其余字节级保留；新增范围识别区分「改标题」与「改正文」，改标题同步回写
outline 使其持久生效（修复改章节标题不生效）；整体性/结构性意见自动回退
整篇重写。前端新增 isRevising：修改时右侧先恢复初始占位（清空旧稿），
重写流到达后实时展示被改章节的流式重写。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

offline-backend-20260512/backend/CLAUDE.md

@@ -278,7 +278,7 @@ Seeding mirrors the roundtable pattern: verified `config.yaml` + `SOUL.md` ship
 
 **Agentic skill execution (`ai_writing.researcher_skill_agent`, default false).** By default a configured non-native skill is *not* run agent-style — the node just turns its `description` into a query for the generic search provider. With this flag on, the directed-skill branch instead runs `nodes/_skill_agent.py::run_skill_search_agent`: it injects the skill's **SKILL.md** (read from `skill.skill_file`) alongside the researcher SOUL as the system prompt, binds a `search` tool to the researcher model, and runs a bounded (`_MAX_TURNS=4`) tool-call loop so the model drives the retrieval per the skill's instructions; the `SearchResult`s the tool returns are harvested directly as materials (no fuzzy text extraction). Requires a tool-calling model; if the model can't tool-call (returns no `tool_calls`) or the agent yields nothing, `_execute_skill` falls back to the legacy description→query search so materials are never empty. The built-in `knowledge-base-search` native concurrent path is unchanged. Tests: `tests/test_ai_writing_skill_agent.py`.
 
-**Targeted user revision (局部修改 — 只改命中章节).** When the user submits a free-text 修改意见 on the draft-confirm card (`action == "user_revise"`), `writer_draft_node` no longer always rewrites the whole article section-by-section. Before the full-rewrite loop it tries `_targeted_user_revision` (`nodes/writer_draft.py`): `_split_draft_sections` parses the previous `current_draft.full_markdown` into `(article_title, [(section_title, body)], references_block)` (level-1 `#` title, level-2 `##` sections, trailing `## 参考文献` pulled out and kept verbatim), then `_detect_revision_scope` runs a small `llm_json` classifier (prompts `DRAFT_REVISE_SCOPE_{SYSTEM,USER}`) that maps the note to the section indices it targets ("第一段/开头/引言"→0, "结尾/结论"→last, by title/topic, etc.). **Only the hit sections are rewritten** via `_stream_revise_section` (prompt `DRAFT_REVISE_SECTION_USER`, streamed as `draft_chunk` so the user watches the edit); **every unhit section is preserved byte-for-byte** and emitted to the stream as one full-text `draft_chunk` + `is_section_done` so the frontend's `streamingDraftSections` rebuilds the complete article (it was reset to `[]` on entering `revising`). The classifier returns `whole_article=true` (整体性意见 like 「整体语气更正式」/「全文都改」, or any structure-changing ask) → `_detect_revision_scope` yields `None` → `_targeted_user_revision` returns `None` → the node **falls back to the existing whole-article rewrite** (which still runs `_revise_outline_with_notes` for title/structure changes). Also falls back when there is no prior draft, an empty note, or scope detection errors. Editor-review revisions (`accept_review`) are unaffected — they keep the holistic rewrite. Reassembly preserves the article title + section structure and re-appends the original references block; word count is computed on the body (excluding references), matching the main path. Tests: `tests/test_ai_writing_targeted_revision.py`.
+**Targeted user revision (局部修改 — 只改命中章节).** When the user submits a free-text 修改意见 on the draft-confirm card (`action == "user_revise"`), `writer_draft_node` no longer always rewrites the whole article section-by-section. Before the full-rewrite loop it tries `_targeted_user_revision` (`nodes/writer_draft.py`): `_split_draft_sections` parses the previous `current_draft.full_markdown` into `(article_title, [(section_title, body)], references_block)` (level-1 `#` title, level-2 `##` sections, trailing `## 参考文献` pulled out and kept verbatim), then `_detect_revision_scope` runs a small `llm_json` classifier (prompts `DRAFT_REVISE_SCOPE_{SYSTEM,USER}`) returning **per-section targets** `[{index, new_title, rewrite_body}]`: it maps the note to the section indices it targets ("第一段/开头/引言"→0, "结尾/结论"→last, by title/topic) **and** distinguishes a **章节标题改名** (`new_title` set, `rewrite_body=false` → rename only, body untouched) from a **正文修改** (`rewrite_body=true`). Title-only renames apply directly to the assembled `## {new_title}` heading **and are written back into `current_outline.sections[i].section_title`** (so the renamed title persists through confirm/finalize/history — this fixes "改章节标题不生效"). Body rewrites run `_stream_revise_section` (prompt `DRAFT_REVISE_SECTION_USER`, streamed as `draft_chunk`). **Only hit sections are touched; unhit sections are preserved byte-for-byte and are NOT re-emitted to the stream** — the frontend clears the right canvas to its initial placeholder on entering `revising` and shows only the live rewrite of the changed section(s), so the user sees「清空 → 流式重写 → 终稿」rather than the whole article rebuilding. The classifier returns `whole_article=true` (整体性意见 like 「整体语气更正式」/「全文都改」, **structure changes** 加章/删章/调整顺序, or a **文章总标题** change) → `_detect_revision_scope` yields `None` → `_targeted_user_revision` returns `None` → the node **falls back to the whole-article rewrite** (which still runs `_revise_outline_with_notes` for title/structure changes). Also falls back when there is no prior draft, an empty note, or scope-detection errors. Editor-review revisions (`accept_review`) keep the holistic rewrite. Reassembly preserves the article title + structure and re-appends the original references block; word count is computed on the body (excluding references). Frontend: `isRevising` in `AIWritingState` (`types/ai-writing.ts`) is set in `useAIWritingStream.ts`'s `intervention_submitted` (`ns === 'revising'`) and cleared on `draft_ready`; `AIWritingDraftPanel.tsx` shows the initial `DraftWaitingPlaceholder` while `isRevising && streamingDraftSections.length === 0`, then the streaming preview once chunks arrive. Tests: `tests/test_ai_writing_targeted_revision.py`.
 
 **History draft editing (历史回看可编辑成稿).** The right-side draft in 历史回看 is no longer read-only — the user can edit it like the live 写作完成态 (Tiptap + 目录 + 格式工具栏 + AI 润色) and **persist** the change back to the session. `PUT /api/ai-writing/sessions/{id}/draft` `{draft_markdown, draft_title?}` (owner-checked → 404 otherwise; `draft_title` omitted ⇒ keep原标题) updates the row via the existing `AIWritingSessionRepository.update`. Frontend: `AIWritingDraftPanel` now passes `readOnly={false}` + an `onSaveDraft` handler (only in history mode) → `TextArtifactRenderer` → `WritingToolbar` 「保存」button (loading + toast); the handler is `AIWritingHistoryContext.saveHistoryDraft(markdown, title?)` → `updateAIWritingDraft` (`api/ai-writing-sessions.ts`), which write-backs the returned summary to `historySession`. Edits to the **live** completed draft stay ephemeral (export-only) as before — only history mode shows 保存. Tests: `tests/test_ai_writing_draft_update.py`.