fix: unstick taking peripherals from an absent peer

[MegaManSec]

Taking peripherals from a locked or sleeping Mac could sit at "Pairing…" for minutes with no way out, while a manual connect from System Settings worked immediately.

• Take-from-peer connects now try openConnection() on the existing bond first (the same cheap connect System Settings does) and only remove + re-pair when the open is refused; the fresh pair pages continuously instead of gating on an RSSI probe an idle Magic device doesn't answer.
• A "Pairing…" row in the dropdown is clickable to cancel the attempt: the attempt token is superseded (in-flight side effects re-check it before doing anything destructive), the pending pair is stopped, and the auto-reconnect watcher is stood down. Cancel is refused while a take's release round trip is still on the wire, so a released peripheral can't be stranded unclaimed.
• A live snapshot now adopts a connect made outside the app while a row shows "Pairing…", instead of holding the stale state until the 60s watchdog fires.

Also fixes a shadowed window check in MenuRowControl.mouseDown that made its stale-row guard a no-op.