fix: WS reconnect leak, refetch on reconnect, error handling

- intentionalClose ref prevents onclose from reconnecting after cleanup
- refetch full history on WS reconnect (catches missed messages)
- onerror handler, try/catch on JSON.parse
- fixes codex review: orphaned sockets, stale closures, missing messages

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/colony/src/App.tsx

@@ -42,13 +42,17 @@ export default function App() {
   // WebSocket: append new messages in real-time
   const handleWsMessage = useCallback((msg: Message) => {
     setMessages((prev) => {
-      // Deduplicate — the sender also fetches after posting
       if (prev.some((m) => m.id === msg.id)) return prev;
       return [...prev, msg];
     });
   }, []);
 
-  useChannelSocket(activeChannelId, handleWsMessage);
+  // On WS reconnect, refetch full history to catch missed messages
+  const handleWsReconnect = useCallback(() => {
+    loadMessages();
+  }, [loadMessages]);
+
+  useChannelSocket(activeChannelId, handleWsMessage, handleWsReconnect);
 
   useEffect(() => { loadChannels(); }, [loadChannels]);