feat(ux): F1 注入面板可控版 — 📌置顶/✕排除/近N章步进器 + 已排除恢复

- injection.ts 加 override 纯函数（currentOverride/withPinToggled/withExcluded/withRestored/withRecentN/isPinned，钳 1..20）+ author_pin 徽标
- useInjection 加 saving 态 + togglePin/exclude/restore/setRecentN，PUT 后以服务端确定结果为准（不变量 #6）；写失败可读文案、不改本地态（天然回滚）
- ChapterAssistant：每实体置顶/排除按钮 + 「近 N 章」步进器 + 「已排除」恢复区
- 13 新 vitest（override 纯函数）；前端门禁绿（lint/tsc/vitest 183/build）

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -1,6 +1,25 @@
 import { describe, expect, it } from "vitest";
 
-import { kindLabel, reasonLabel } from "./injection";
+import {
+  currentOverride,
+  isPinned,
+  kindLabel,
+  reasonLabel,
+  withExcluded,
+  withPinToggled,
+  withRecentN,
+  withRestored,
+  type InjectionOverrideRequest,
+  type InjectionResponse,
+} from "./injection";
+
+const REF = { kind: "character", name: "林动" } as const;
+
+const emptyOverride = (): InjectionOverrideRequest => ({
+  pinned: [],
+  excluded: [],
+  recent_n: 5,
+});
 
 describe("reasonLabel", () => {
   it("maps each known selection reason to a Chinese badge", () => {
@@ -8,6 +27,7 @@ describe("reasonLabel", () => {
     expect(reasonLabel("main_character")).toBe("主角常驻");
     expect(reasonLabel("recent_digest")).toBe("近章出现");
     expect(reasonLabel("foreshadow_window")).toBe("伏笔窗口");
+    expect(reasonLabel("author_pin")).toBe("作者置顶");
   });
 
   it("falls back to the raw code for an unknown reason", () => {
@@ -25,3 +45,59 @@ describe("kindLabel", () => {
     expect(kindLabel("mystery")).toBe("mystery");
   });
 });
+
+describe("currentOverride", () => {
+  it("extracts pinned/excluded/recent_n from a response", () => {
+    const data = {
+      project_id: "p",
+      chapter_no: 1,
+      selected: [],
+      recent_n: 3,
+      pinned: [REF],
+      excluded: [{ kind: "world_entity", name: "玄铁" }],
+    } as unknown as InjectionResponse;
+    expect(currentOverride(data)).toEqual({
+      pinned: [REF],
+      excluded: [{ kind: "world_entity", name: "玄铁" }],
+      recent_n: 3,
+    });
+  });
+});
+
+describe("withPinToggled", () => {
+  it("pins an unpinned ref and removes it from excluded", () => {
+    const next = withPinToggled(withExcluded(emptyOverride(), REF), REF);
+    expect(isPinned(next, REF)).toBe(true);
+    expect(next.excluded).toEqual([]);
+  });
+
+  it("unpins an already-pinned ref", () => {
+    const pinned = withPinToggled(emptyOverride(), REF);
+    const next = withPinToggled(pinned, REF);
+    expect(isPinned(next, REF)).toBe(false);
+  });
+});
+
+describe("withExcluded / withRestored", () => {
+  it("excludes a ref, removing it from pinned, then restores it", () => {
+    const pinnedThenExcluded = withExcluded(withPinToggled(emptyOverride(), REF), REF);
+    expect(isPinned(pinnedThenExcluded, REF)).toBe(false);
+    expect(pinnedThenExcluded.excluded).toEqual([REF]);
+    const restored = withRestored(pinnedThenExcluded, REF);
+    expect(restored.excluded).toEqual([]);
+  });
+
+  it("is idempotent when excluding twice", () => {
+    const once = withExcluded(emptyOverride(), REF);
+    const twice = withExcluded(once, REF);
+    expect(twice.excluded).toEqual([REF]);
+  });
+});
+
+describe("withRecentN", () => {
+  it("clamps below the minimum and above the maximum", () => {
+    expect(withRecentN(emptyOverride(), 0).recent_n).toBe(1);
+    expect(withRecentN(emptyOverride(), 999).recent_n).toBe(20);
+    expect(withRecentN(emptyOverride(), 7).recent_n).toBe(7);
+  });
+});