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.ts

@@ -5,13 +5,21 @@ import type { components } from "@/lib/api/schema";
 
 export type InjectionResponse = components["schemas"]["InjectionResponse"];
 export type InjectionEntity = components["schemas"]["InjectionEntity"];
+export type InjectionEntityRef = components["schemas"]["InjectionEntityRef"];
+export type InjectionOverrideRequest =
+  components["schemas"]["InjectionOverrideRequest"];
 
-// SelectionReason → 作者可读徽标（对齐 ARCH §3.4 的四来源）。
+// recent_n 合法区间（与后端 RECENT_N_MIN/MAX 对齐；越界后端 422）。
+export const RECENT_N_MIN = 1;
+export const RECENT_N_MAX = 20;
+
+// SelectionReason → 作者可读徽标（对齐 ARCH §3.4 的四来源 + 作者置顶）。
 export const REASON_LABELS: Record<string, string> = {
   explicit_beat: "本章点名",
   main_character: "主角常驻",
   recent_digest: "近章出现",
   foreshadow_window: "伏笔窗口",
+  author_pin: "作者置顶",
 };
 
 // EntityKind → 中文。
@@ -28,3 +36,81 @@ export function reasonLabel(reason: string): string {
 export function kindLabel(kind: string): string {
   return KIND_LABELS[kind] ?? kind;
 }
+
+// ---- 作者覆盖（B0 可控版）纯函数：从响应推导当前覆盖 + 不可变地施加单个改动 ----
+
+const refKey = (r: InjectionEntityRef): string => `${r.kind}:${r.name}`;
+const sameRef = (a: InjectionEntityRef, b: InjectionEntityRef): boolean =>
+  a.kind === b.kind && a.name === b.name;
+
+// 从注入响应回显字段抽出当前覆盖（PUT 回放服务端确定结果后驱动 UI）。
+export function currentOverride(
+  data: InjectionResponse,
+): InjectionOverrideRequest {
+  return {
+    pinned: [...(data.pinned ?? [])],
+    excluded: [...(data.excluded ?? [])],
+    recent_n: data.recent_n,
+  };
+}
+
+export function isPinned(
+  override: InjectionOverrideRequest,
+  ref: InjectionEntityRef,
+): boolean {
+  return (override.pinned ?? []).some((r) => sameRef(r, ref));
+}
+
+const without = (
+  list: InjectionEntityRef[] | undefined,
+  ref: InjectionEntityRef,
+): InjectionEntityRef[] => (list ?? []).filter((r) => !sameRef(r, ref));
+
+// 切换 pin：已置顶 → 取消；否则置顶并从排除列表移除（一个实体不同时 pin+排除）。
+export function withPinToggled(
+  override: InjectionOverrideRequest,
+  ref: InjectionEntityRef,
+): InjectionOverrideRequest {
+  const pinnedNow = isPinned(override, ref);
+  return {
+    ...override,
+    pinned: pinnedNow
+      ? without(override.pinned, ref)
+      : [...(override.pinned ?? []), { kind: ref.kind, name: ref.name }],
+    excluded: without(override.excluded, ref),
+  };
+}
+
+// 排除：加入排除列表，并从置顶列表移除。重复排除幂等（先去重再加）。
+export function withExcluded(
+  override: InjectionOverrideRequest,
+  ref: InjectionEntityRef,
+): InjectionOverrideRequest {
+  return {
+    ...override,
+    pinned: without(override.pinned, ref),
+    excluded: [
+      ...without(override.excluded, ref),
+      { kind: ref.kind, name: ref.name },
+    ],
+  };
+}
+
+// 恢复被排除的实体（回到纯自动选择判定）。
+export function withRestored(
+  override: InjectionOverrideRequest,
+  ref: InjectionEntityRef,
+): InjectionOverrideRequest {
+  return { ...override, excluded: without(override.excluded, ref) };
+}
+
+// 设置近况回看章数（钳到合法区间，避免后端 422）。
+export function withRecentN(
+  override: InjectionOverrideRequest,
+  n: number,
+): InjectionOverrideRequest {
+  const clamped = Math.max(RECENT_N_MIN, Math.min(RECENT_N_MAX, Math.round(n)));
+  return { ...override, recent_n: clamped };
+}
+
+export { refKey };