feat(backend): 整章再沟通/重写 SSE 端点——喂当前草稿+意见+完整记忆注入流式重写一版

WFW-8 整章级再沟通（后端）。新增 POST /projects/{id}/chapters/{no}/rewrite（SSE）：
- rewrite.md 教条（品类无关内核，非 SPEC，仿 write_craft 经 load_prompt 读盘）；
- rewrite_node：build_rewrite_request 纯函数（system=[rewrite教条,stable_core] cache 前缀；
  input=近况+当前草稿+作者意见，断点后不入缓存前缀——守不变量 #9）+ stream_chapter_rewrite；
- RewriteStreamRequest{feedback,prior_draft}（带 max_length 上界）；端点复用 assemble 记忆注入
  + normalize_deltas SSE，只读不写库（HITL，新版停前端接受才落，不变量 #3），是工具非写节点
  （不破坏 章=f(outline,state) 纯函数，不变量 #7），项目不存在触网关前 404。

门禁绿：ruff / mypy 224 files / pytest（新增 test_rewrite_node 5 例 + 更新 doctrine 一一对应）/
alembic 无漂移。OpenAPI 含新路径 + schema（前端待 gen:api）。

apps/api/ww_api/routers/projects.py

@@ -37,6 +37,7 @@ from ww_core.orchestrator import (
     normalize_deltas,
     normalize_review,
     stream_chapter_draft,
+    stream_chapter_rewrite,
 )
 from ww_db import get_session
 from ww_llm_gateway import Gateway
@@ -63,6 +64,7 @@ from ww_api.schemas.projects import (
     ReviewHistoryItem,
     ReviewHistoryResponse,
     ReviewRequest,
+    RewriteStreamRequest,
 )
 from ww_api.services.accept_service import (
     AcceptOutcome,
@@ -310,6 +312,64 @@ async def stream_draft(
     )
 
 
+@router.post("/{project_id}/chapters/{chapter_no}/rewrite")
+async def stream_rewrite(
+    project_id: uuid.UUID,
+    chapter_no: int,
+    request: Request,
+    repos: MemoryReposDep,
+    gateway: GatewayDep,
+    injection_repo: InjectionRepoDep,
+    project_repo: ProjectRepoDep,
+    session: Annotated[AsyncSession, Depends(get_session)],
+    body: RewriteStreamRequest,
+) -> StreamingResponse:
+    """整章再沟通/重写：组装记忆 + 当前草稿 + 作者意见 → 网关流 → 归一 SSE → event-stream。
+
+    HITL：新版停前端/草稿，接受才落库（不变量 #3）；rewrite 是工具非写节点，不破坏章
+    纯函数性（不变量 #7）。项目不存在 → 404（触网关前 fail-fast，同 draft，QA C1）。
+    """
+    if await project_repo.get(STUB_OWNER_ID, project_id) is None:
+        raise AppError(ErrorCode.NOT_FOUND, f"project not found: {project_id}")
+    request_id = getattr(request.state, "request_id", None)
+    override = await injection_repo.get(project_id, chapter_no)
+    context = await assemble(repos, project_id, chapter_no, override=override)
+    log.info(
+        "rewrite_stream_start",
+        project_id=str(project_id),
+        chapter_no=chapter_no,
+        request_id=request_id,
+        stable_core_len=len(context.stable_core),
+        volatile_len=len(context.volatile),
+        prior_draft_len=len(body.prior_draft),
+        feedback_len=len(body.feedback),
+    )
+
+    deltas = stream_chapter_rewrite(
+        gateway,
+        stable_core=context.stable_core,
+        volatile=context.volatile,
+        prior_draft=body.prior_draft,
+        feedback=body.feedback,
+        user_id=STUB_OWNER_ID,
+        project_id=project_id,
+    )
+
+    async def _frames() -> AsyncIterator[str]:
+        async for event in normalize_deltas(deltas, request_id=request_id):
+            yield _encode_sse(event)
+        try:
+            await session.commit()
+        except Exception:  # noqa: BLE001 — 流已发完，commit 失败不能再改响应；至少记错误。
+            log.error("sse_commit_failed", request_id=request_id, endpoint="rewrite")
+
+    return StreamingResponse(
+        _frames(),
+        media_type="text/event-stream",
+        headers={"cache-control": "no-cache", "x-accel-buffering": "no"},
+    )
+
+
 @router.put("/{project_id}/chapters/{chapter_no}/draft")
 async def save_draft(
     project_id: uuid.UUID,