refactor(frontend): 抽出可复用 ConversationThread + inlineConversation 纯助手

把 AiConversationDrawer 内联的气泡渲染（Bubble/readOptions/ACCEPT_LABEL）提取为
共享的 ConversationThread 组件，抽屉改为复用之（外观不变，DRY）。新增纯助手
lib/workbench/inlineConversation.ts：mergeInlineThreads（已落库留痕 ∪ 进行中气泡，
按 id 去重 + 复用 groupByThread 定序）、toPendingView（合成未落库气泡，meta._pending/
_streaming UI 标记）、isPendingView/isStreamingView/readSegment，配 9 单测（RED→GREEN）。
为内联对话视图铺路；抽屉行为完全不变。

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

@@ -0,0 +1,122 @@
+import { describe, expect, it } from "vitest";
+
+import type { AiMessageView } from "@/lib/api/types";
+import {
+  PENDING_CREATED_AT,
+  isPendingView,
+  isStreamingView,
+  mergeInlineThreads,
+  readSegment,
+  toPendingView,
+} from "./inlineConversation";
+
+// AiMessageView 工厂：只填测试关心的字段，其余给稳定默认（对齐 aiConversation.test.ts）。
+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("mergeInlineThreads", () => {
+  it("只保留本章 + 指定 kinds 的已落库消息", () => {
+    const persisted = [
+      view({ thread_id: "a", chapter_no: 1, kind: "refine", seq: 0 }),
+      view({ thread_id: "b", chapter_no: 2, kind: "refine", seq: 0 }), // 他章
+      view({ thread_id: "c", chapter_no: 1, kind: "continue", seq: 0 }), // 他 kind
+    ];
+    const threads = mergeInlineThreads(persisted, 1, ["refine", "clarify"], []);
+    expect(threads.map((t) => t.threadId)).toEqual(["a"]);
+  });
+
+  it("并入进行中气泡（按 id 去重、已落库优先），排在本章会话末尾", () => {
+    const persisted = [
+      view({ id: "p1", thread_id: "s", chapter_no: 1, kind: "refine", seq: 0, role: "author", content: "原文" }),
+      view({ id: "p2", thread_id: "s", chapter_no: 1, kind: "refine", seq: 1, role: "ai", content: "第一版" }),
+    ];
+    const pending = [
+      toPendingView({ localId: "pend-a", role: "author", content: "再改" }, { threadId: "s", chapterNo: 1, kind: "refine", seq: 0 }),
+      toPendingView({ localId: "pend-b", role: "ai", content: "", streaming: true }, { threadId: "s", chapterNo: 1, kind: "refine", seq: 1 }),
+    ];
+    const threads = mergeInlineThreads(persisted, 1, ["refine"], pending);
+    expect(threads).toHaveLength(1);
+    expect(threads[0]!.messages.map((m) => m.id)).toEqual(["p1", "p2", "pend-a", "pend-b"]);
+  });
+
+  it("进行中气泡 id 与已落库重复时不重复（已落库优先）", () => {
+    const persisted = [view({ id: "dup", thread_id: "s", chapter_no: 1, kind: "refine", seq: 0 })];
+    const pending = [
+      toPendingView({ localId: "dup", role: "ai", content: "x" }, { threadId: "s", chapterNo: 1, kind: "refine", seq: 9 }),
+    ];
+    const threads = mergeInlineThreads(persisted, 1, ["refine"], pending);
+    expect(threads[0]!.messages).toHaveLength(1);
+    expect(threads[0]!.messages[0]!.id).toBe("dup");
+  });
+
+  it("无已落库时进行中气泡自成一线程", () => {
+    const pending = [
+      toPendingView({ localId: "x", role: "author", content: "hi" }, { threadId: "new", chapterNo: 1, kind: "rewrite", seq: 0 }),
+    ];
+    const threads = mergeInlineThreads([], 1, ["rewrite"], pending);
+    expect(threads).toHaveLength(1);
+    expect(threads[0]!.messages[0]!.id).toBe("x");
+  });
+
+  it("空输入 → 空数组", () => {
+    expect(mergeInlineThreads([], 1, ["refine"], [])).toEqual([]);
+  });
+});
+
+describe("toPendingView", () => {
+  it("合成未落库气泡：meta._pending，映射 role/content/kind/seq，created_at 恒为未来常量", () => {
+    const v = toPendingView(
+      { localId: "L1", role: "ai", content: "改写中", streaming: true },
+      { threadId: "t9", chapterNo: 3, kind: "rewrite", seq: 2 },
+    );
+    expect(v.id).toBe("L1");
+    expect(v.role).toBe("ai");
+    expect(v.content).toBe("改写中");
+    expect(v.thread_id).toBe("t9");
+    expect(v.chapter_no).toBe(3);
+    expect(v.kind).toBe("rewrite");
+    expect(v.seq).toBe(2);
+    expect(v.created_at).toBe(PENDING_CREATED_AT);
+    expect(isPendingView(v)).toBe(true);
+    expect(isStreamingView(v)).toBe(true);
+  });
+
+  it("非流式种子不带 _streaming", () => {
+    const v = toPendingView(
+      { localId: "L2", role: "author", content: "x" },
+      { threadId: "t", chapterNo: 1, kind: "refine", seq: 0 },
+    );
+    expect(isStreamingView(v)).toBe(false);
+    expect(isPendingView(v)).toBe(true);
+  });
+});
+
+describe("isPendingView / isStreamingView", () => {
+  it("已落库消息（无标记）均为 false", () => {
+    const v = view({});
+    expect(isPendingView(v)).toBe(false);
+    expect(isStreamingView(v)).toBe(false);
+  });
+});
+
+describe("readSegment", () => {
+  it("取 meta.segment 字符串；缺失/非串回退空串", () => {
+    expect(readSegment({ segment: "原选段" })).toBe("原选段");
+    expect(readSegment({})).toBe("");
+    expect(readSegment({ segment: 42 })).toBe("");
+    expect(readSegment(undefined)).toBe("");
+  });
+});