sendGate property
When set, send PARKS (after counting/recording) until this gate completes — the sibling of proposeGate for the sign+broadcast half. The harness for anything that has to happen WHILE a send is in flight: leaving the screen mid-submit, stacking a second entry over a running send, or releasing the landing afterwards to prove it wrote nothing it shouldn't.
Implementation
Completer<void>? sendGate;