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/useInjection.ts

@@ -1,24 +1,40 @@
 "use client";
 
-import { useEffect, useState } from "react";
+import { useCallback, useEffect, useState } from "react";
 
 import { api } from "@/lib/api/client";
-import type { InjectionResponse } from "./injection";
+import {
+  currentOverride,
+  withExcluded,
+  withPinToggled,
+  withRecentN,
+  withRestored,
+  type InjectionEntityRef,
+  type InjectionOverrideRequest,
+  type InjectionResponse,
+} from "./injection";
 
 export interface UseInjection {
   data: InjectionResponse | null;
   loading: boolean;
+  saving: boolean;
   error: string | null;
+  togglePin: (ref: InjectionEntityRef) => Promise<void>;
+  exclude: (ref: InjectionEntityRef) => Promise<void>;
+  restore: (ref: InjectionEntityRef) => Promise<void>;
+  setRecentN: (n: number) => Promise<void>;
 }
 
-// 本章注入透明（B0 读端点）：挂载时拉一次确定性 SelectionTrace。
-// 只读、无 LLM、无 commit——展示「选了谁/为什么」。失败给可读文案不抛。
-export function useInjection(
-  projectId: string,
-  chapterNo: number,
-): UseInjection {
+const INJECTION_PATH =
+  "/projects/{project_id}/chapters/{chapter_no}/injection" as const;
+
+// 本章注入透明（B0 可控版）：读确定性 SelectionTrace + 作者覆盖；
+// pin/排除/recent_n 经 PUT 覆盖 → 服务端回放新的确定结果（看到的=写章用的）。
+// 写失败给可读文案、不改本地状态（天然回滚），不抛。
+export function useInjection(projectId: string, chapterNo: number): UseInjection {
   const [data, setData] = useState<InjectionResponse | null>(null);
   const [loading, setLoading] = useState(true);
+  const [saving, setSaving] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
   useEffect(() => {
@@ -27,10 +43,9 @@ export function useInjection(
     setError(null);
 
     void (async () => {
-      const { data: body, error: err } = await api.GET(
-        "/projects/{project_id}/chapters/{chapter_no}/injection",
-        { params: { path: { project_id: projectId, chapter_no: chapterNo } } },
-      );
+      const { data: body, error: err } = await api.GET(INJECTION_PATH, {
+        params: { path: { project_id: projectId, chapter_no: chapterNo } },
+      });
       if (cancelled) return;
       if (err || !body) {
         setError("注入信息暂不可用");
@@ -46,5 +61,49 @@ export function useInjection(
     };
   }, [projectId, chapterNo]);
 
-  return { data, loading, error };
+  const save = useCallback(
+    async (override: InjectionOverrideRequest) => {
+      setSaving(true);
+      setError(null);
+      const { data: body, error: err } = await api.PUT(INJECTION_PATH, {
+        params: { path: { project_id: projectId, chapter_no: chapterNo } },
+        body: override,
+      });
+      if (err || !body) {
+        setError("保存注入设置失败，请重试");
+      } else {
+        setData(body); // 以服务端确定结果为准（不变量 #6）。
+      }
+      setSaving(false);
+    },
+    [projectId, chapterNo],
+  );
+
+  const mutate = useCallback(
+    (fn: (o: InjectionOverrideRequest) => InjectionOverrideRequest) =>
+      async (): Promise<void> => {
+        if (!data) return;
+        await save(fn(currentOverride(data)));
+      },
+    [data, save],
+  );
+
+  const togglePin = useCallback(
+    (ref: InjectionEntityRef) => mutate((o) => withPinToggled(o, ref))(),
+    [mutate],
+  );
+  const exclude = useCallback(
+    (ref: InjectionEntityRef) => mutate((o) => withExcluded(o, ref))(),
+    [mutate],
+  );
+  const restore = useCallback(
+    (ref: InjectionEntityRef) => mutate((o) => withRestored(o, ref))(),
+    [mutate],
+  );
+  const setRecentN = useCallback(
+    (n: number) => mutate((o) => withRecentN(o, n))(),
+    [mutate],
+  );
+
+  return { data, loading, saving, error, togglePin, exclude, restore, setRecentN };
 }