After a WebSocket disconnect, the daemon's view of running tasks and
workspace state can lag the server for up to 5s (per-task cancellation
poll) or 30s (workspace sync) because both loops park on coarse tickers
that do not observe the WS wakeup channel.
This change adds a small fan-out broadcaster (`reconcileBroadcaster`)
that the WS connect path fires once per (re)connect. `watchTaskCancellation`
and `workspaceSyncLoop` subscribe and re-check immediately on broadcast,
without disturbing the ticker cadence. The broadcaster is edge-triggered
with a one-slot replay so a broadcast that lands before a subscriber is
ready is not lost (closes the daemon-startup race), and back-to-back
broadcasts inside 1s are debounced so a flapping connection cannot fan
out into a request stampede.
Existing behaviour is preserved: shouldInterruptAgent still decides
whether to interrupt, the 5s/30s ticker still bounds the worst case,
and the WS heartbeat / HTTP heartbeat coordination is untouched.
Closes#4665
