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/components/workbench/Workbench.tsx

@@ -0,0 +1,156 @@
+"use client";
+
+import Link from "next/link";
+import { useEffect, useRef, useState } from "react";
+
+import { AppShell } from "@/components/AppShell";
+import type { ProjectResponse } from "@/lib/api/types";
+import { useAutosave } from "@/lib/autosave/useAutosave";
+import { useDraftStream } from "@/lib/stream/useDraftStream";
+import { ChapterList } from "./ChapterList";
+import { ChapterAssistant } from "./ChapterAssistant";
+import { Editor } from "./Editor";
+
+interface WorkbenchProps {
+  project: ProjectResponse;
+}
+
+// M1：单章工作台。章节列表为占位（无章节列表端点）；默认第 1 章。
+const M1_CHAPTER_NO = 1;
+
+export function Workbench({ project }: WorkbenchProps) {
+  const chapterNo = M1_CHAPTER_NO;
+  const [text, setText] = useState("");
+  const autosave = useAutosave(project.id, chapterNo);
+  const stream = useDraftStream();
+  const lastStreamText = useRef("");
+
+  // 流式 token 累积进编辑器（打字机）；停止/结束后已生成部分留在草稿。
+  useEffect(() => {
+    const streamed = stream.state.text;
+    if (
+      (stream.state.phase === "streaming" ||
+        stream.state.phase === "done" ||
+        stream.state.phase === "aborted") &&
+      streamed !== lastStreamText.current
+    ) {
+      lastStreamText.current = streamed;
+      setText(streamed);
+      autosave.onChange(streamed);
+    }
+  }, [stream.state.phase, stream.state.text, autosave]);
+
+  const onWrite = (): void => {
+    void stream.start(project.id, chapterNo);
+  };
+
+  const onEditorChange = (value: string): void => {
+    setText(value);
+    autosave.onChange(value);
+  };
+
+  const wordCount = text.length;
+
+  return (
+    <AppShell
+      title={`〈${project.title}〉`}
+      subtitle={`第 ${chapterNo} 章`}
+    >
+      <div className="grid h-[calc(100vh-4rem)] grid-cols-1 lg:grid-cols-[12rem_1fr_18rem]">
+        <ChapterList currentChapterNo={chapterNo} />
+
+        <section className="flex min-w-0 flex-col bg-bg">
+          <div className="flex-1 overflow-auto px-6 py-8">
+            <Editor
+              value={text}
+              onChange={onEditorChange}
+              streaming={stream.isStreaming}
+            />
+          </div>
+          <Toolbar
+            projectId={project.id}
+            chapterNo={chapterNo}
+            wordCount={wordCount}
+            savedLabel={autosave.savedLabel}
+            saveStatus={autosave.status}
+            streaming={stream.isStreaming}
+            streamError={stream.state.error}
+            onWrite={onWrite}
+            onStop={stream.stop}
+          />
+        </section>
+
+        <ChapterAssistant />
+      </div>
+    </AppShell>
+  );
+}
+
+interface ToolbarProps {
+  projectId: string;
+  chapterNo: number;
+  wordCount: number;
+  savedLabel: string | null;
+  saveStatus: ReturnType<typeof useAutosave>["status"];
+  streaming: boolean;
+  streamError: { code: string; message: string } | null;
+  onWrite: () => void;
+  onStop: () => void;
+}
+
+function Toolbar({
+  projectId,
+  chapterNo,
+  wordCount,
+  savedLabel,
+  saveStatus,
+  streaming,
+  streamError,
+  onWrite,
+  onStop,
+}: ToolbarProps) {
+  return (
+    <div className="border-t border-line bg-panel px-6 py-3">
+      {streamError ? (
+        <p className="mb-2 text-sm text-conflict">
+          写章失败（{streamError.code}）：{streamError.message}
+        </p>
+      ) : null}
+      <div className="flex items-center gap-4">
+        {streaming ? (
+          <button
+            type="button"
+            onClick={onStop}
+            className="rounded border border-conflict px-4 py-2 text-sm text-conflict"
+          >
+            停
+          </button>
+        ) : (
+          <button
+            type="button"
+            onClick={onWrite}
+            className="rounded bg-cinnabar px-4 py-2 text-sm text-panel hover:opacity-90"
+          >
+            ✍ 写本章
+          </button>
+        )}
+        <span className="font-mono text-xs text-ink-soft">
+          字数 {wordCount.toLocaleString()}
+        </span>
+        <Link
+          href={`/projects/${projectId}/review?chapter=${chapterNo}`}
+          className="rounded border border-cinnabar px-4 py-2 text-sm text-cinnabar hover:bg-[var(--color-cinnabar-wash)]"
+        >
+          审稿 →
+        </Link>
+        <span className="ml-auto font-mono text-xs text-ink-soft">
+          {saveStatus === "saving"
+            ? "保存中…"
+            : saveStatus === "error"
+              ? "保存失败"
+              : (savedLabel ?? "尚未保存")}
+        </span>
+      </div>
+    </div>
+  );
+}