Three fixes:
- Persist claude_pane via thalamus extra map so it survives every
save path (not just explicit Save commands)
- Don't clobber claude_pane with empty string when TMUX_PANE is unset
- signal_response now passes TMUX_PANE like signal_user does
- maybe_prompt_notification returns early when user is present,
preventing notification spam during active sessions
Co-Authored-By: Proof of Concept <poc@bcachefs.org>
