feat(messenger): group settings UI — rename, member list, add/remove

- messenger-api: useGroupSettings(threadId) — members query + rename/add/
  remove commands + isAdmin (from the member roles); live + mock
- messenger: a settings (gear) button on group thread headers opens a
  GroupSettingsModal — editable name (admin), member list with role pills,
  admin-gated remove, and add-from-directory search
- controls are admin-gated in the UI; IIOS/OPA re-enforces server-side

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/messenger-api.ts

@@ -87,12 +87,26 @@ export interface ThreadData {
   refetch: () => void;
 }
 
+export interface UiMember { userId: string; displayName: string; role: string }
+export interface GroupSettingsData {
+  loading: boolean; error: string | null;
+  members: UiMember[];
+  isAdmin: boolean;
+  rename: (subject: string) => Promise<void>;
+  addMember: (userId: string) => Promise<void>;
+  removeMember: (userId: string) => Promise<void>;
+  refetch: () => void;
+}
+
 export function useMessengerData(): MessengerData {
   return SHELL ? useLiveMessenger() : useMockMessenger();
 }
 export function useThread(threadId: string): ThreadData {
   return SHELL ? useLiveThread(threadId) : useMockThread(threadId);
 }
+export function useGroupSettings(threadId: string): GroupSettingsData {
+  return SHELL ? useLiveGroupSettings(threadId) : useMockGroupSettings(threadId);
+}
 
 /* ======================================================================== */
 /* Live implementation (be-crm data door + IIOS socket)                     */
@@ -259,6 +273,29 @@ function useLiveThread(threadId: string): ThreadData {
   };
 }
 
+function useLiveGroupSettings(threadId: string): GroupSettingsData {
+  const { sdk } = useAppShell();
+  const { user } = useAuth();
+  const q = useQuery<UiMember[]>("crm.messenger.members", { threadId });
+  const members = useMemo(() => q.data ?? [], [q.data]);
+  const isAdmin = useMemo(() => members.some((m) => m.userId === user?.id && m.role === "ADMIN"), [members, user?.id]);
+
+  const rename = useCallback(async (subject: string) => {
+    await sdk.command("crm.messenger.group.rename", { threadId, subject });
+    q.refetch();
+  }, [sdk, threadId, q]);
+  const addMember = useCallback(async (userId: string) => {
+    await sdk.command("crm.messenger.participant.add", { threadId, userId });
+    q.refetch();
+  }, [sdk, threadId, q]);
+  const removeMember = useCallback(async (userId: string) => {
+    await sdk.command("crm.messenger.participant.remove", { threadId, userId });
+    q.refetch();
+  }, [sdk, threadId, q]);
+
+  return { loading: q.loading, error: q.error?.message ?? null, members, isAdmin, rename, addMember, removeMember, refetch: q.refetch };
+}
+
 function shape(
   c: ConversationDTO,
   nameOf: (id: string) => string,
@@ -372,3 +409,27 @@ function useMockThread(threadId: string): ThreadData {
     typingUserIds: [], seenIds: new Set(), refetch: notifyMock,
   };
 }
+
+function useMockGroupSettings(threadId: string): GroupSettingsData {
+  useMockSubscription();
+  const nameById = useMemo(() => Object.fromEntries(MOCK_PEOPLE.map((p) => [p.id, p.name])), []);
+  const t = MOCK_STORE.get(threadId);
+  const members: UiMember[] = (t?.participants ?? []).map((id) => ({
+    userId: id,
+    displayName: id === "me" ? "You" : (nameById[id] ?? `User ${shortId(id)}`),
+    role: id === "me" ? "ADMIN" : "MEMBER",
+  }));
+  const rename = useCallback(async (subject: string) => {
+    const th = MOCK_STORE.get(threadId);
+    if (th) { th.subject = subject; notifyMock(); }
+  }, [threadId]);
+  const addMember = useCallback(async (userId: string) => {
+    const th = MOCK_STORE.get(threadId);
+    if (th && !th.participants.includes(userId)) { th.participants = [...th.participants, userId]; notifyMock(); }
+  }, [threadId]);
+  const removeMember = useCallback(async (userId: string) => {
+    const th = MOCK_STORE.get(threadId);
+    if (th) { th.participants = th.participants.filter((p) => p !== userId); notifyMock(); }
+  }, [threadId]);
+  return { loading: false, error: null, members, isAdmin: true, rename, addMember, removeMember, refetch: notifyMock };
+}