feat: 标签管理功能 + 问答前缀对用户隐藏

标签管理:
- 新增 tags/tag_assignments 持久化层、迁移、/api/tags 路由
- 标签分智能体/技能/定时任务三类, 仅同类型可互打, 仅 admin 可增删改与打标签
- 三类资源列表支持按名称模糊检索与按标签筛选(走后端查询参数)
- 前端新增标签管理页、TagPickerDialog(点击即时绑定)、彩色标签 chip

问答前缀:
- 前缀不再拼入消息 content, 改存 additional_kwargs 由 PromptPrefixMiddleware
  在调模型前临时注入, 用户界面看不到前缀但模型仍收到
- 修正 thread_existed 闸门导致首轮前缀被跳过的问题

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend-web/src/components/workspace/settings/skill-settings-page.tsx

@@ -12,6 +12,7 @@ import {
   PinIcon,
   PinOffIcon,
   SparklesIcon,
+  TagsIcon,
   Trash2Icon,
   TrendingUpIcon,
   Upload,
@@ -46,6 +47,9 @@ import {
   ItemDescription,
 } from "@/components/ui/item";
 import { Tabs, TabsList, TabsTrigger } from "@/components/ui/tabs";
+import { TagChipList } from "@/components/workspace/tags/tag-chip";
+import { TagPickerDialog } from "@/components/workspace/tags/tag-picker-dialog";
+import { TagSearchBar } from "@/components/workspace/tags/tag-search-bar";
 import { getStoredAuth } from "@/core/auth";
 import { useI18n } from "@/core/i18n/hooks";
 import type { ValidateSkillUploadResponse } from "@/core/skills/api";
@@ -66,36 +70,27 @@ import { SkillStateSheet } from "./skill-state-sheet";
 
 export function SkillSettingsPage({ onClose }: { onClose?: () => void } = {}) {
   const { t } = useI18n();
-  const { skills, isLoading, error } = useSkills();
   return (
     <SettingsSection
       title={t.settings.skills.title}
       description={t.settings.skills.description}
     >
-      {isLoading ? (
-        <div className="text-muted-foreground text-sm">{t.common.loading}</div>
-      ) : error ? (
-        <div>Error: {error.message}</div>
-      ) : (
-        <SkillSettingsList skills={skills} onClose={onClose} />
-      )}
+      <SkillSettingsList onClose={onClose} />
     </SettingsSection>
   );
 }
 
-function SkillSettingsList({
-  skills,
-  onClose,
-}: {
-  skills: Skill[];
-  onClose?: () => void;
-}) {
+function SkillSettingsList({ onClose }: { onClose?: () => void }) {
   const { t } = useI18n();
   const router = useRouter();
   const [filter, setFilter] = useState<string>("all");
   const [installOpen, setInstallOpen] = useState(false);
   const [staleSheetOpen, setStaleSheetOpen] = useState(false);
   const [archiveSheetOpen, setArchiveSheetOpen] = useState(false);
+  const [search, setSearch] = useState("");
+  const [tagId, setTagId] = useState<string | null>(null);
+  // Name + tag filtering is resolved server-side via the /api/skills query.
+  const { skills, isLoading, error } = useSkills({ search, tagId });
 
   const storedAuth = useMemo(() => getStoredAuth(), []);
   const currentUserId = storedAuth?.user_id ?? null;
@@ -211,10 +206,22 @@ function SkillSettingsList({
           </Button>
         </div>
       </header>
-      {filteredSkills.length === 0 && (
+      <TagSearchBar
+        targetType="skill"
+        onSearchChange={setSearch}
+        tagId={tagId}
+        onTagIdChange={setTagId}
+        className="max-w-xl"
+      />
+      {isLoading && (
+        <div className="text-muted-foreground text-sm">{t.common.loading}</div>
+      )}
+      {error && <div className="text-destructive text-sm">Error: {error.message}</div>}
+      {!isLoading && !error && filteredSkills.length === 0 && (
         <EmptySkill onCreateSkill={handleCreateSkill} />
       )}
-      {filteredSkills.length > 0 &&
+      {!isLoading && !error &&
+        filteredSkills.length > 0 &&
         filteredSkills.map((skill) => (
           <SkillRow
             key={skill.name}
@@ -258,6 +265,7 @@ function SkillRow({
   const setPinned = useSetSkillPinned();
   const deleteSkill = useDeleteCustomSkill();
   const [confirmDeleteOpen, setConfirmDeleteOpen] = useState(false);
+  const [tagPickerOpen, setTagPickerOpen] = useState(false);
 
   const isCustom = skill.category === "custom";
   // Built-in flag falls back to "no DB owner" so legacy responses without
@@ -392,8 +400,22 @@ function SkillRow({
                 : t.settings.skills.useCountInlineZero}
             </div>
           )}
+          {(skill.tags?.length ?? 0) > 0 && (
+            <TagChipList tags={skill.tags!} className="mt-2" />
+          )}
         </ItemContent>
         <ItemActions>
+          {isAdmin && (
+            <Button
+              size="icon"
+              variant="ghost"
+              className="h-8 w-8 shrink-0"
+              onClick={() => setTagPickerOpen(true)}
+              title={t.adminTags.manageTags}
+            >
+              <TagsIcon className="size-3.5" />
+            </Button>
+          )}
           {canManage && (
             <Button
               size="icon"
@@ -473,6 +495,15 @@ function SkillRow({
           </DialogFooter>
         </DialogContent>
       </Dialog>
+      {isAdmin && (
+        <TagPickerDialog
+          open={tagPickerOpen}
+          onOpenChange={setTagPickerOpen}
+          targetType="skill"
+          targetId={skill.name}
+          currentTags={skill.tags ?? []}
+        />
+      )}
     </>
   );
 }