feat(11-03): add skill groups frontend API client and query keys

- Create ui/src/api/skillGroups.ts with skillGroupsApi object
- All 14 methods covering group CRUD, members, export/import, agent assignments
- removeGroup uses raw fetch for DELETE-with-body (api.delete has no body support)
- Add skillGroups namespace to ui/src/lib/queryKeys.ts with 6 key factories

ui/src/api/skillGroups.ts

@@ -0,0 +1,93 @@
+import { api, ApiError } from "./client";
+
+export type SkillGroupRow = {
+  id: string;
+  name: string;
+  description: string | null;
+  isBuiltin: number;
+  createdAt: number;
+  updatedAt: number;
+};
+
+export type GroupMemberRow = {
+  groupId: string;
+  skillId: string;
+  addedAt: number;
+};
+
+export type AssignResult = {
+  installed: string[];
+  skipped: string[];
+  pendingPlugin: string[];
+};
+
+export type GroupExport = {
+  version: "1";
+  group: {
+    id: string;
+    name: string;
+    description: string | null;
+    members: string[];
+    parents: string[];
+  };
+};
+
+export const skillGroupsApi = {
+  listGroups: () => api.get<SkillGroupRow[]>("/skill-registry/groups"),
+
+  getGroup: (groupId: string) =>
+    api.get<SkillGroupRow>(`/skill-registry/groups/${groupId}`),
+
+  createGroup: (input: { name: string; description?: string }) =>
+    api.post<SkillGroupRow>("/skill-registry/groups", input),
+
+  updateGroup: (groupId: string, patch: { name?: string; description?: string }) =>
+    api.patch<SkillGroupRow>(`/skill-registry/groups/${groupId}`, patch),
+
+  deleteGroup: (groupId: string) =>
+    api.delete<void>(`/skill-registry/groups/${groupId}`),
+
+  listMembers: (groupId: string) =>
+    api.get<GroupMemberRow[]>(`/skill-registry/groups/${groupId}/members`),
+
+  addMember: (groupId: string, skillId: string) =>
+    api.post<{ ok: boolean }>(`/skill-registry/groups/${groupId}/members`, { skillId }),
+
+  removeMember: (groupId: string, skillId: string) =>
+    api.delete<void>(`/skill-registry/groups/${groupId}/members/${skillId}`),
+
+  exportGroup: (groupId: string) =>
+    api.get<GroupExport>(`/skill-registry/groups/${groupId}/export`),
+
+  importGroup: (data: GroupExport) =>
+    api.post<SkillGroupRow>("/skill-registry/groups/import", data),
+
+  listAgentGroups: (agentId: string) =>
+    api.get<SkillGroupRow[]>(`/skill-registry/agents/${agentId}/groups`),
+
+  assignGroup: (agentId: string, groupId: string, agentSkillsDir: string) =>
+    api.post<AssignResult>(`/skill-registry/agents/${agentId}/groups`, {
+      groupId,
+      agentSkillsDir,
+    }),
+
+  removeGroup: async (agentId: string, groupId: string, agentSkillsDir: string): Promise<void> => {
+    const res = await fetch(`/api/skill-registry/agents/${agentId}/groups/${groupId}`, {
+      method: "DELETE",
+      credentials: "include",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ agentSkillsDir }),
+    });
+    if (!res.ok && res.status !== 204) {
+      const errorBody = await res.json().catch(() => null);
+      throw new ApiError(
+        (errorBody as { error?: string } | null)?.error ?? `Request failed: ${res.status}`,
+        res.status,
+        errorBody,
+      );
+    }
+  },
+
+  listAgentSkills: (agentId: string) =>
+    api.get<string[]>(`/skill-registry/agents/${agentId}/skills`),
+};

ui/src/lib/queryKeys.ts

@@ -138,6 +138,14 @@ export const queryKeys = {
     detail: (skillId: string) => ["skill-registry", "skills", skillId] as const,
     versions: (skillId: string) => ["skill-registry", "skills", skillId, "versions"] as const,
   },
+  skillGroups: {
+    list: ["skill-groups"] as const,
+    detail: (groupId: string) => ["skill-groups", groupId] as const,
+    members: (groupId: string) => ["skill-groups", groupId, "members"] as const,
+    agentGroups: (agentId: string) => ["skill-groups", "agent", agentId] as const,
+    agentSkills: (agentId: string) => ["skill-groups", "agent", agentId, "skills"] as const,
+    agentEffective: (agentId: string) => ["skill-groups", "agent", agentId, "effective"] as const,
+  },
   plugins: {
     all: ["plugins"] as const,
     examples: ["plugins", "examples"] as const,