fix(15): prevent infinite loop in chat history fetch

The useEffect condition allowed fetching when fetchStatus was 'failed',
causing infinite retry loops when the API returned an error.

Changed condition from:
  fetchStatus !== 'loading' && fetchStatus !== 'succeeded'
To:
  fetchStatus === 'idle'

This ensures we only fetch once per channel on initial load, and don't
retry automatically on failure.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

jam-ui/src/components/client/chat/JKChatMessageList.js

@@ -127,10 +127,13 @@ const JKChatMessageList = () => {
 
   /**
    * Fetch chat history when channel becomes active
-   * Only fetches if we haven't fetched yet for this channel
+   * Only fetches once per channel (when status is 'idle')
+   * Does NOT retry on failure to avoid infinite loops
    */
   useEffect(() => {
-    if (activeChannel && fetchStatus !== 'loading' && fetchStatus !== 'succeeded') {
+    // Only fetch when status is 'idle' (initial state)
+    // This prevents infinite loops on API failure ('failed' status)
+    if (activeChannel && fetchStatus === 'idle') {
       // For session chat, activeChannel is the sessionId
       // Pass sessionId so the thunk knows to fetch 'session' channel type
       dispatch(fetchChatHistory({