feat: M1 — 立项→写章草稿(SSE)→自动保存；连一家 provider

- 薄自建 LLM 网关：OpenAI 兼容适配器(DeepSeek) + instructor 结构化输出 + usage_ledger 记账 + 档位路由
- 记忆服务 assemble：确定性选择(显式+主角+近况) + 渲染卡 + 缓存断点(中性文本)
- LangGraph 写章节点 + Postgres checkpointer + SSE 归一(token/done/error)
- API：立项 + 写章 draft(SSE) + PUT 自动保存 + 提供商凭据(Fernet 加密/测试连接)
- 前端：AppShell + 作品库 + 5 步立项向导 + 写作工作台(流式打字机+自动保存) + 设置页
- M1 E2E：真实 DB + mock 网关零 token 走通闭环

apps/web/lib/stream/sse.test.ts

@@ -0,0 +1,96 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  SseFrameBuffer,
+  initialStreamState,
+  parseSseBlock,
+  reduceStream,
+  type SseEvent,
+} from "./sse";
+
+describe("parseSseBlock", () => {
+  it("parses a token frame", () => {
+    const evt = parseSseBlock('event:token\ndata:{"text":"夜"}');
+    expect(evt).toEqual({ event: "token", data: { text: "夜" } });
+  });
+
+  it("parses a done frame", () => {
+    const evt = parseSseBlock('event:done\ndata:{"length":12}');
+    expect(evt).toEqual({ event: "done", data: { length: 12 } });
+  });
+
+  it("parses an error frame with request_id", () => {
+    const evt = parseSseBlock(
+      'event:error\ndata:{"code":"INTERNAL","message":"boom","request_id":"r1"}',
+    );
+    expect(evt).toEqual({
+      event: "error",
+      data: { code: "INTERNAL", message: "boom", request_id: "r1" },
+    });
+  });
+
+  it("ignores comment/heartbeat lines and tolerates leading space after colon", () => {
+    const evt = parseSseBlock(': keep-alive\nevent: token\ndata: {"text":"x"}');
+    expect(evt).toEqual({ event: "token", data: { text: "x" } });
+  });
+
+  it("returns null for unknown event types", () => {
+    expect(parseSseBlock('event:section\ndata:{"x":1}')).toBeNull();
+  });
+
+  it("returns null for malformed json", () => {
+    expect(parseSseBlock("event:token\ndata:{not json")).toBeNull();
+  });
+});
+
+describe("SseFrameBuffer", () => {
+  it("emits complete blocks split by blank line and buffers the tail", () => {
+    const buf = new SseFrameBuffer();
+    const first = buf.push('event:token\ndata:{"text":"a"}\n\nevent:tok');
+    expect(first).toEqual([{ event: "token", data: { text: "a" } }]);
+    const second = buf.push('en\ndata:{"text":"b"}\n\n');
+    expect(second).toEqual([{ event: "token", data: { text: "b" } }]);
+  });
+
+  it("handles CRLF boundaries", () => {
+    const buf = new SseFrameBuffer();
+    const out = buf.push('event:token\r\ndata:{"text":"z"}\r\n\r\n');
+    expect(out).toEqual([{ event: "token", data: { text: "z" } }]);
+  });
+});
+
+describe("reduceStream", () => {
+  it("accumulates token text and marks streaming", () => {
+    const tokens: SseEvent[] = [
+      { event: "token", data: { text: "夜色" } },
+      { event: "token", data: { text: "如墨" } },
+    ];
+    const state = tokens.reduce(reduceStream, initialStreamState);
+    expect(state.text).toBe("夜色如墨");
+    expect(state.phase).toBe("streaming");
+  });
+
+  it("marks done on done event preserving text", () => {
+    let s = reduceStream(initialStreamState, {
+      event: "token",
+      data: { text: "abc" },
+    });
+    s = reduceStream(s, { event: "done", data: { length: 3 } });
+    expect(s.phase).toBe("done");
+    expect(s.text).toBe("abc");
+  });
+
+  it("captures error and retains partial text", () => {
+    let s = reduceStream(initialStreamState, {
+      event: "token",
+      data: { text: "partial" },
+    });
+    s = reduceStream(s, {
+      event: "error",
+      data: { code: "LLM_UNAVAILABLE", message: "no key" },
+    });
+    expect(s.phase).toBe("error");
+    expect(s.text).toBe("partial");
+    expect(s.error?.code).toBe("LLM_UNAVAILABLE");
+  });
+});

apps/web/lib/stream/sse.ts

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+// SSE 帧解析 + 草稿流归一（对齐 C3 / ARCH §7.3）。
+// 帧格式：`event:<token|done|error>\ndata:<json>\n\n`。
+// 纯逻辑，便于单测（不依赖浏览器/DOM）。
+
+export interface TokenEvent {
+  event: "token";
+  data: { text: string };
+}
+export interface DoneEvent {
+  event: "done";
+  data: { length: number };
+}
+export interface ErrorEvent {
+  event: "error";
+  data: { code: string; message: string; request_id?: string | null };
+}
+export type SseEvent = TokenEvent | DoneEvent | ErrorEvent;
+
+const KNOWN_EVENTS = new Set(["token", "done", "error"]);
+
+// 把一个完整 SSE 块（多行）解析成事件；无法解析则返回 null（跳过）。
+export function parseSseBlock(block: string): SseEvent | null {
+  let event = "";
+  const dataLines: string[] = [];
+  for (const rawLine of block.split("\n")) {
+    const line = rawLine.replace(/\r$/, "");
+    if (line.startsWith(":")) continue; // 注释/心跳
+    const sep = line.indexOf(":");
+    if (sep === -1) continue;
+    const field = line.slice(0, sep);
+    const value = line.slice(sep + 1).replace(/^ /, "");
+    if (field === "event") event = value;
+    else if (field === "data") dataLines.push(value);
+  }
+  if (!KNOWN_EVENTS.has(event) || dataLines.length === 0) return null;
+  let data: unknown;
+  try {
+    data = JSON.parse(dataLines.join("\n"));
+  } catch {
+    return null;
+  }
+  return { event, data } as SseEvent;
+}
+
+// 增量缓冲：吃进一段文本，吐出已完成的事件块（以空行分隔），保留未完成尾部。
+export class SseFrameBuffer {
+  private buf = "";
+
+  push(chunk: string): SseEvent[] {
+    this.buf += chunk;
+    const events: SseEvent[] = [];
+    let idx: number;
+    // 块之间以空行（\n\n，兼容 \r\n\r\n）分隔。
+    while ((idx = this.findBoundary(this.buf)) !== -1) {
+      const block = this.buf.slice(0, idx.valueOf());
+      this.buf = this.buf.slice(this.boundaryEnd(this.buf, idx));
+      const evt = parseSseBlock(block);
+      if (evt) events.push(evt);
+    }
+    return events;
+  }
+
+  private findBoundary(s: string): number {
+    const a = s.indexOf("\n\n");
+    const b = s.indexOf("\r\n\r\n");
+    if (a === -1) return b;
+    if (b === -1) return a;
+    return Math.min(a, b);
+  }
+
+  private boundaryEnd(s: string, idx: number): number {
+    return s.startsWith("\r\n\r\n", idx) ? idx + 4 : idx + 2;
+  }
+}
+
+export type StreamPhase = "idle" | "streaming" | "done" | "error" | "aborted";
+
+export interface StreamState {
+  phase: StreamPhase;
+  text: string;
+  error: { code: string; message: string; request_id?: string | null } | null;
+}
+
+export const initialStreamState: StreamState = {
+  phase: "idle",
+  text: "",
+  error: null,
+};
+
+// 纯 reducer：把单个事件折叠进状态（打字机文本累积）。
+export function reduceStream(state: StreamState, event: SseEvent): StreamState {
+  switch (event.event) {
+    case "token":
+      return {
+        ...state,
+        phase: "streaming",
+        text: state.text + event.data.text,
+      };
+    case "done":
+      return { ...state, phase: "done" };
+    case "error":
+      return { ...state, phase: "error", error: event.data };
+    default:
+      return state;
+  }
+}

apps/web/lib/stream/useDraftStream.ts

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+"use client";
+
+import { useCallback, useReducer, useRef } from "react";
+
+import { API_BASE_PUBLIC } from "@/lib/api/config";
+import {
+  SseFrameBuffer,
+  initialStreamState,
+  reduceStream,
+  type StreamState,
+} from "./sse";
+
+type Action =
+  | { type: "start" }
+  | { type: "events"; events: ReturnType<SseFrameBuffer["push"]> }
+  | { type: "abort" }
+  | { type: "fail"; code: string; message: string }
+  | { type: "reset"; text: string };
+
+function reducer(state: StreamState, action: Action): StreamState {
+  switch (action.type) {
+    case "start":
+      return { phase: "streaming", text: "", error: null };
+    case "events":
+      return action.events.reduce(reduceStream, state);
+    case "abort":
+      return { ...state, phase: "aborted" };
+    case "fail":
+      return {
+        ...state,
+        phase: "error",
+        error: { code: action.code, message: action.message },
+      };
+    case "reset":
+      return { ...initialStreamState, text: action.text };
+    default:
+      return state;
+  }
+}
+
+export interface UseDraftStream {
+  state: StreamState;
+  isStreaming: boolean;
+  start: (projectId: string, chapterNo: number) => Promise<void>;
+  stop: () => void;
+  reset: (text: string) => void;
+}
+
+// 消费 POST .../draft 的 SSE 流。用 fetch+ReadableStream（EventSource 不支持 POST）。
+// "停" = abort 连接（已生成部分保留在 state.text，由调用方落入草稿）。
+export function useDraftStream(): UseDraftStream {
+  const [state, dispatch] = useReducer(reducer, initialStreamState);
+  const controllerRef = useRef<AbortController | null>(null);
+
+  const stop = useCallback(() => {
+    controllerRef.current?.abort();
+    controllerRef.current = null;
+    dispatch({ type: "abort" });
+  }, []);
+
+  const reset = useCallback((text: string) => {
+    dispatch({ type: "reset", text });
+  }, []);
+
+  const start = useCallback(async (projectId: string, chapterNo: number) => {
+    const controller = new AbortController();
+    controllerRef.current = controller;
+    dispatch({ type: "start" });
+    try {
+      const res = await fetch(
+        `${API_BASE_PUBLIC}/projects/${projectId}/chapters/${chapterNo}/draft`,
+        {
+          method: "POST",
+          headers: { Accept: "text/event-stream" },
+          signal: controller.signal,
+        },
+      );
+      if (!res.ok || !res.body) {
+        // 流前错误（如无凭据 → 503 LLM_UNAVAILABLE，JSON 信封而非帧）。
+        let code = "STREAM_FAILED";
+        let message = `写章请求失败（${res.status}）`;
+        try {
+          const body = (await res.json()) as {
+            error?: { code?: string; message?: string };
+          };
+          if (body.error?.code) code = body.error.code;
+          if (body.error?.message) message = body.error.message;
+        } catch {
+          // 非 JSON 信封，沿用默认文案。
+        }
+        dispatch({ type: "fail", code, message });
+        return;
+      }
+      const reader = res.body.getReader();
+      const decoder = new TextDecoder();
+      const buffer = new SseFrameBuffer();
+      for (;;) {
+        const { value, done } = await reader.read();
+        if (done) break;
+        const events = buffer.push(decoder.decode(value, { stream: true }));
+        if (events.length > 0) dispatch({ type: "events", events });
+      }
+    } catch (err: unknown) {
+      if (err instanceof DOMException && err.name === "AbortError") {
+        // 用户主动停止：state 已置 aborted。
+        return;
+      }
+      const message = err instanceof Error ? err.message : "未知网络错误";
+      dispatch({ type: "fail", code: "NETWORK", message });
+    } finally {
+      controllerRef.current = null;
+    }
+  }, []);
+
+  return {
+    state,
+    isStreaming: state.phase === "streaming",
+    start,
+    stop,
+    reset,
+  };
+}