Fixes "Cannot access 'mobileSyncPanelOpen' before initialization" when triggering My Magnetar sync.
Shared panel state now initializes before sync handlers and asynchronous startup. Early returns on pages without detected magnets no longer leave sync controls with uninitialized state. Chrome and Firefox include the same fix.
Pairing, encryption, stored data, settings, styling and layout are unchanged.
Validation: all 41 automated checks pass; eight Chromium UI scenarios pass using both content-script versions with simulated background responses. Connected-device sync was not tested.
Assets: Chrome ZIP and unsigned Firefox XPI.