feat(frontend): AI 对话核心——视图模型 + 数据/追加 hook + 抽屉（AC-3）

- lib/workbench/aiConversation.ts：纯视图模型（kind 标签/徽标、bubbleSide、
  按 thread 归组 (created_at,seq) 定序、按作用域分区、接受动作映射）+ 单测。
- lib/workbench/useAiConversation.ts：Workbench 级懒加载 + 批量 append（乐观插入 +
  正位对账 / 失败回滚），fail-soft 绝不 throw 进生成/HITL；silent 直投供工具箱页。
  renderHook 测试覆盖懒加载去重、对账、回滚、silent、项目切换复位。
- components/workbench/AiConversationDrawer.tsx：本章对话 + 项目级生成两段的气泡抽屉，
  克隆 ContextDrawer 的 a11y（role=dialog/log、Esc、focus trap、还原焦点）；
  ai 气泡挂 DRAFT-only 再接受按钮（替换整章/插入正文/回填选段），不绕开验收事务。
- lib/api/types.ts：re-export AiMessage* 码生成名。

apps/web/lib/workbench/aiConversation.test.ts

@@ -0,0 +1,135 @@
+import { describe, expect, it } from "vitest";
+
+import type { AiMessageView } from "@/lib/api/types";
+import {
+  acceptActionFor,
+  bubbleSide,
+  groupByThread,
+  KIND_LABEL,
+  kindLabel,
+  partitionByScope,
+} from "./aiConversation";
+
+// AiMessageView 工厂：只填测试关心的字段，其余给稳定默认。
+function view(partial: Partial<AiMessageView>): AiMessageView {
+  return {
+    id: partial.id ?? crypto.randomUUID(),
+    project_id: "p1",
+    chapter_no: partial.chapter_no ?? null,
+    thread_id: partial.thread_id ?? "t1",
+    seq: partial.seq ?? 0,
+    kind: partial.kind ?? "refine",
+    tool_key: partial.tool_key ?? null,
+    role: partial.role ?? "ai",
+    content: partial.content ?? "",
+    meta: partial.meta ?? {},
+    created_at: partial.created_at ?? "2026-07-09T00:00:00Z",
+  };
+}
+
+describe("kindLabel / KIND_LABEL", () => {
+  it("五类 kind 各有中文标签", () => {
+    expect(KIND_LABEL.refine).toBe("润色");
+    expect(KIND_LABEL.rewrite).toBe("整章重写");
+    expect(KIND_LABEL.clarify).toBe("反问澄清");
+    expect(KIND_LABEL.continue).toBe("续写");
+    expect(KIND_LABEL.generator).toBe("工具箱");
+  });
+
+  it("未知 kind 回退为原始串（不崩）", () => {
+    expect(kindLabel("mystery")).toBe("mystery");
+    expect(kindLabel("refine")).toBe("润色");
+  });
+});
+
+describe("bubbleSide", () => {
+  it("author 靠右、ai 靠左", () => {
+    expect(bubbleSide("author")).toBe("right");
+    expect(bubbleSide("ai")).toBe("left");
+  });
+});
+
+describe("groupByThread", () => {
+  it("按 thread_id 归组，返回每组 kind/toolKey/chapterNo", () => {
+    const msgs = [
+      view({ thread_id: "a", kind: "refine", chapter_no: 1, seq: 0 }),
+      view({ thread_id: "b", kind: "continue", tool_key: "continue", chapter_no: 1, seq: 0 }),
+      view({ thread_id: "a", kind: "refine", chapter_no: 1, seq: 1 }),
+    ];
+    const threads = groupByThread(msgs);
+    const a = threads.find((t) => t.threadId === "a");
+    expect(a?.messages).toHaveLength(2);
+    expect(a?.kind).toBe("refine");
+    const b = threads.find((t) => t.threadId === "b");
+    expect(b?.toolKey).toBe("continue");
+    expect(b?.chapterNo).toBe(1);
+  });
+
+  it("同一批次 created_at 相同时，按 seq 升序排组内（不靠 created_at 单独定序）", () => {
+    // 故意乱序传入；同 created_at，靠 seq 稳定定序。
+    const msgs = [
+      view({ thread_id: "a", seq: 2, content: "c2", created_at: "2026-07-09T00:00:00Z" }),
+      view({ thread_id: "a", seq: 0, content: "c0", created_at: "2026-07-09T00:00:00Z" }),
+      view({ thread_id: "a", seq: 1, content: "c1", created_at: "2026-07-09T00:00:00Z" }),
+    ];
+    const thread = groupByThread(msgs)[0]!;
+    expect(thread.messages.map((m) => m.content)).toEqual(["c0", "c1", "c2"]);
+  });
+
+  it("跨批次靠 created_at 定序，组内新批 append 在后", () => {
+    const msgs = [
+      view({ thread_id: "a", seq: 0, content: "old", created_at: "2026-07-09T00:00:00Z" }),
+      view({ thread_id: "a", seq: 0, content: "new", created_at: "2026-07-09T00:05:00Z" }),
+    ];
+    const thread = groupByThread(msgs)[0]!;
+    expect(thread.messages.map((m) => m.content)).toEqual(["old", "new"]);
+  });
+
+  it("线程按各自首条 (created_at, seq) 升序（老线程在前）", () => {
+    const msgs = [
+      view({ thread_id: "late", seq: 0, created_at: "2026-07-09T01:00:00Z" }),
+      view({ thread_id: "early", seq: 0, created_at: "2026-07-09T00:00:00Z" }),
+    ];
+    const threads = groupByThread(msgs);
+    expect(threads.map((t) => t.threadId)).toEqual(["early", "late"]);
+  });
+
+  it("空输入 → 空数组", () => {
+    expect(groupByThread([])).toEqual([]);
+  });
+});
+
+describe("partitionByScope", () => {
+  it("本章线程与项目级(chapter_no=null)线程分区", () => {
+    const msgs = [
+      view({ thread_id: "chap", chapter_no: 3, seq: 0 }),
+      view({ thread_id: "proj", chapter_no: null, kind: "generator", seq: 0 }),
+    ];
+    const threads = groupByThread(msgs);
+    const { chapterThreads, projectThreads } = partitionByScope(threads, 3);
+    expect(chapterThreads.map((t) => t.threadId)).toEqual(["chap"]);
+    expect(projectThreads.map((t) => t.threadId)).toEqual(["proj"]);
+  });
+
+  it("非本章号的章线程不落入本章分区（联合查询兜底）", () => {
+    const threads = groupByThread([
+      view({ thread_id: "other", chapter_no: 9, seq: 0 }),
+    ]);
+    const { chapterThreads, projectThreads } = partitionByScope(threads, 3);
+    expect(chapterThreads).toHaveLength(0);
+    expect(projectThreads).toHaveLength(0);
+  });
+});
+
+describe("acceptActionFor", () => {
+  it("按 kind 映射接受动作；clarify/未知无动作", () => {
+    const mk = (kind: string) =>
+      groupByThread([view({ thread_id: kind, kind, seq: 0 })])[0]!;
+    expect(acceptActionFor(mk("rewrite"))).toBe("replace_chapter");
+    expect(acceptActionFor(mk("continue"))).toBe("append_draft");
+    expect(acceptActionFor(mk("generator"))).toBe("append_draft");
+    expect(acceptActionFor(mk("refine"))).toBe("refill_segment");
+    expect(acceptActionFor(mk("clarify"))).toBeNull();
+    expect(acceptActionFor(mk("mystery"))).toBeNull();
+  });
+});