refactor(15-01): clean up debug logging in WebSocket handler

- Remove console.log for received WebSocket messages
- Remove console.log for Redux dispatch
- Remove console.log for callback registration
- WebSocket handler verified: extracts all attachment fields correctly

jam-ui/src/components/client/JKSessionScreen.js

@@ -573,7 +573,6 @@ const JKSessionScreen = () => {
         // Chat message handler - receives messages from WebSocket and dispatches to Redux
         // Callback signature: (fullMessage, payload) where payload contains the chat_message data
         const handleChatMessage = (fullMessage, payload) => {
-          console.log('[CHAT DEBUG] Received WebSocket message:', payload);
           // Transform Protocol Buffer format to Redux format
           // payload contains: {sender_name, sender_id, msg, msg_id, created_at, channel, ...}
           const message = {
@@ -591,7 +590,6 @@ const JKSessionScreen = () => {
             attachmentName: payload.attachment_name, // filename
             attachmentSize: payload.attachment_size  // file size in bytes (may be null)
           };
-          console.log('[CHAT DEBUG] Dispatching to Redux:', message);
           dispatch(addMessageFromWebSocket(message));
         };
 
@@ -606,9 +604,6 @@ const JKSessionScreen = () => {
 
         callbacksToRegister.forEach(({ type, callback }) => {
           registerMessageCallback(type, callback);
-          if (type === MessageType.CHAT_MESSAGE) {
-            console.log('[CHAT DEBUG] Registered CHAT_MESSAGE callback for session:', currentSession.id);
-          }
         });
 
         // Store registered callbacks for cleanup