The agent backgrounds $D serve (Claude Code can't block on a subprocess
and do other work simultaneously). With stdout-only feedback delivery,
the agent never sees regenerate/remix feedback.
Fix: write feedback-pending.json (regenerate/remix) and feedback.json
(submit) to disk next to the board HTML. Agent polls the filesystem
instead of reading stdout. Both channels (stdout + disk) are always
active so foreground mode still works.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>