Improve error_message diagnostics from Letta agent

Extract useful attributes from error_message chunks instead of
logging the unhelpful default string representation. Dumps all
non-None attributes if standard fields are empty.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[e-mail]>

bsky.py

···
                         # Indent response text
                         for line in chunk.content.split('\n'):
                             print(f"  {line}")
+                    elif chunk.message_type == 'error_message':
+                        # Extract all available error info
+                        error_details = []
+                        for attr in ['content', 'message', 'error', 'reason', 'details', 'run_id', 'step_id']:
+                            val = getattr(chunk, attr, None)
+                            if val:
+                                error_details.append(f"{attr}={val}")
+                        if error_details:
+                            logger.error(f"Agent error: {', '.join(error_details)}")
+                        else:
+                            # Dump all non-None attributes
+                            all_attrs = {k: v for k, v in vars(chunk).items() if v is not None and not k.startswith('_')}
+                            logger.error(f"Agent error (raw): {all_attrs}")
+                        # Also log full object at debug level
+                        logger.debug(f"Full error_message: {chunk}")
                     else:
                         # Filter out verbose message types
                         if chunk.message_type not in ['usage_statistics', 'stop_reason']:
···
                     print("  ──────────────────")
                     for line in chunk.content.split('\n'):
                         print(f"  {line}")
-            
+                elif chunk.message_type == 'error_message':
+                    # Extract all available error info
+                    error_details = []
+                    for attr in ['content', 'message', 'error', 'reason', 'details', 'run_id', 'step_id']:
+                        val = getattr(chunk, attr, None)
+                        if val:
+                            error_details.append(f"{attr}={val}")
+                    if error_details:
+                        logger.error(f"Synthesis error: {', '.join(error_details)}")
+                    else:
+                        all_attrs = {k: v for k, v in vars(chunk).items() if v is not None and not k.startswith('_')}
+                        logger.error(f"Synthesis error (raw): {all_attrs}")
+
             if str(chunk) == 'done':
                 break