The auto-continue logic was adding User continue prompts without first
adding an Assistant message when the LLM returned an empty response.
This caused consecutive User messages in the conversation history,
which confused the LLM and caused it to return more empty responses.
The fix ensures an Assistant message is always added before the continue
prompt, using '[empty response]' as a placeholder when the LLM returned
nothing substantive. This maintains proper User/Assistant alternation.
fe96969adb