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）。

packages/core/tests/test_rewrite_node.py

@@ -0,0 +1,95 @@
+"""整章重写节点单测：纯构造 + 转发网关 Delta（注入 mock 网关，无图运行时、无 DB）。
+
+守不变量 ②（只声明 tier=writer）/#9（rewrite 教条 + stable_core 进缓存前缀，草稿/意见进
+断点后 input，不入缓存前缀）。asyncio_mode=auto。
+"""
+
+from __future__ import annotations
+
+import uuid
+from collections.abc import AsyncIterator
+
+from ww_core.orchestrator import (
+    build_rewrite_input,
+    build_rewrite_request,
+    stream_chapter_rewrite,
+)
+from ww_llm_gateway.types import Delta, LlmRequest
+
+
+class _FakeGateway:
+    """记录收到的请求并按给定文本吐 Delta。"""
+
+    def __init__(self, texts: list[str]) -> None:
+        self._texts = texts
+        self.last_req: LlmRequest | None = None
+
+    async def stream(self, req: LlmRequest) -> AsyncIterator[Delta]:
+        self.last_req = req
+        for text in self._texts:
+            yield Delta(text=text)
+
+
+def test_build_rewrite_input_orders_volatile_draft_feedback() -> None:
+    out = build_rewrite_input(volatile="近况X", prior_draft="草稿Y", feedback="意见Z")
+    assert "【当前整章草稿】" in out
+    assert "【作者意见】" in out
+    # 顺序：近况 → 草稿 → 意见。
+    assert out.index("近况X") < out.index("草稿Y") < out.index("意见Z")
+
+
+def test_build_rewrite_input_omits_empty_volatile() -> None:
+    out = build_rewrite_input(volatile="   ", prior_draft="D", feedback="F")
+    assert out.startswith("【当前整章草稿】")
+    assert "D" in out and "F" in out
+
+
+def test_build_rewrite_request_declares_writer_tier_and_streams() -> None:
+    req = build_rewrite_request(
+        stable_core="SC",
+        volatile="V",
+        prior_draft="DRAFT",
+        feedback="FEEDBACK",
+        user_id=uuid.uuid4(),
+        project_id=uuid.uuid4(),
+    )
+    assert req.tier == "writer"  # 不变量 ②
+    assert req.stream is True
+
+
+def test_rewrite_cached_prefix_excludes_draft_and_feedback() -> None:
+    """不变量 #9：草稿/意见是逐轮易变，绝不进 system 缓存前缀，只进断点后 input。"""
+    req = build_rewrite_request(
+        stable_core="STABLE_CORE",
+        volatile="V",
+        prior_draft="THE_DRAFT_BODY",
+        feedback="THE_FEEDBACK",
+        user_id=uuid.uuid4(),
+        project_id=uuid.uuid4(),
+    )
+    cached_prefix = "".join(block.text for block in req.system)
+    assert all(block.cache for block in req.system)
+    assert "STABLE_CORE" in cached_prefix
+    assert "THE_DRAFT_BODY" not in cached_prefix
+    assert "THE_FEEDBACK" not in cached_prefix
+    assert "THE_DRAFT_BODY" in req.input
+    assert "THE_FEEDBACK" in req.input
+
+
+async def test_stream_chapter_rewrite_forwards_gateway_deltas() -> None:
+    gateway = _FakeGateway(["新版一", "新版二"])
+    out = [
+        delta.text
+        async for delta in stream_chapter_rewrite(
+            gateway,
+            stable_core="SC",
+            volatile="V",
+            prior_draft="D",
+            feedback="F",
+            user_id=uuid.uuid4(),
+            project_id=uuid.uuid4(),
+        )
+    ]
+    assert out == ["新版一", "新版二"]
+    assert gateway.last_req is not None
+    assert gateway.last_req.tier == "writer"