New OfflineState global mirrored from the shared engine by a status
forwarder task. Login screen: start-offline link gated on a previous
session existing, connectivity-down callout pointing at it (with captive
portal hint), init-error callout fed from the restore flow. Shell: D2
recovery banner (connection back during an unauthenticated offline
session) with one-click token sign-in that lifts the offline gate for the
login attempt and re-enters the full online shell.
Double-init hardening for the recovery path re-running enter_shell over a
live shell: synchronous guard on the Linux tray init (its OnceLock was set
asynchronously, leaving a duplicate-tray window) and a start guard on the
playback poll loop (a second loop would double-advance the queue).
cc
vicrodh
38e0b4be27