feat: add auto-follow supervisor with auto-stop

[ChengTu-Lazy]

Summary

• add UI-level auto-follow that can automatically reply to ask_user prompts and continue after a turn completes
• add "auto-stop on done" so the supervisor can disable auto-follow when the task is complete
• preserve structured ask_user payloads and use assistant revision tracking to avoid repeated-text dedupe bugs

Validation

• python -m py_compile agentmain.py frontends/stapp.py launch.pyw self_supervisor.py
• verified ask_user extraction with both structured loop_result and rendered tool-log samples