feat(messaging-ui): message timestamps + group/channel settings panel (0.1.5)

- Every message now shows a Slack-style time (clock today, then 'Yesterday',
  weekday, else a date; full timestamp on hover).
- New ConversationSettings panel for groups AND channels (public + private):
  rename, member list, add people (from the directory), remove, and leave.
  Opened from a new thread header gear; DMs show no gear. Adapter gains
  addMember/removeMember/renameConversation (optional, OPA still gates writes).

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

packages/iios-messaging-ui/src/components/messenger.tsx

@@ -34,6 +34,7 @@ export function Messenger() {
 
   const channels = useMemo(() => conversations.filter((c) => c.membership === 'channel'), [conversations]);
   const dms = useMemo(() => conversations.filter((c) => c.membership !== 'channel'), [conversations]);
+  const selectedConversation = useMemo(() => conversations.find((c) => c.threadId === selected) ?? null, [conversations, selected]);
 
   function pick(threadId: string): void {
     setBrowsing(false);
@@ -104,7 +105,16 @@ export function Messenger() {
             }}
           />
         ) : (
-          <Thread threadId={selected} activeRootId={activeRoot} onOpenThread={setActiveRoot} />
+          <Thread
+            threadId={selected}
+            conversation={selectedConversation}
+            activeRootId={activeRoot}
+            onOpenThread={setActiveRoot}
+            onLeft={() => {
+              refetch();
+              setSelected(null);
+            }}
+          />
         )}
       </section>