fix(agent): log outer-loop exceptions at ERROR with traceback (#32264)

The outer 'except Exception' guard in run_conversation() captures
exceptions raised inside the agent loop (during streaming, tool
dispatch, message construction, etc.) and prints a one-line summary
to the screen.  The traceback was only logged at DEBUG, so it never
landed in errors.log (WARNING+) and was lost.

For intermittent failures — the most important kind to debug — users
saw 'Error during OpenAI-compatible API call #N: <message>' on
screen with no way to recover the call site.  Switching to
logger.exception() emits the full traceback at ERROR so it goes to
both agent.log and errors.log automatically.

This is a pure logging change; control flow is unchanged.

agent/conversation_loop.py

@@ -3945,8 +3945,14 @@ def run_conversation(
                 print(f"❌ {error_msg}")
             except (OSError, ValueError):
                 logger.error(error_msg)
-            
-            logger.debug("Outer loop error in API call #%d", api_call_count, exc_info=True)
+
+            # Emit the full traceback at ERROR level so it lands in both
+            # agent.log AND errors.log.  Previously this was logged at DEBUG,
+            # which meant intermittent outer-loop failures were unreproducible
+            # — users would see a one-line summary on screen with no way to
+            # recover the call site.  logger.exception() includes the
+            # traceback automatically and emits at ERROR.
+            logger.exception("Outer loop error in API call #%d", api_call_count)
             
             # If an assistant message with tool_calls was already appended,
             # the API expects a role="tool" result for every tool_call_id.