bridge: between resync-park and answer recognition, busy=false lets an unrelated message start a concurrent run on the suspended session

[bigduu]

Pre-existing narrow window noted while fixing #9 (PR #11): after resync_pending_asks parks an ask, busy stays false until an answer is matched — an unrelated inbound message in that window is routed as a new run on a session that is still suspended server-side. Consider marking the chat busy (or queueing inbound) while a parked ask exists. Filed by the automated loop, 2026-07-16.