waitForUpdateToFinish kept the parked run's identity (marker line 2 and the
stable run id) as local state in main.ts and threaded both into
reportHandoffResult. That correlation is update behaviour, so it moves to
update-handoff-report.ts as parkedRunReport(): park(marker) on every live
marker the gate sees, report(host) once the wait ends, matching the result
to the last parked run. main.ts keeps only the composition calls and is
three lines shorter than the parent PR's main.ts.
8bb74e0413