Drop the pairing page and the OnActivated / OnDeactivating
lifecycle hooks. Keep the Toolbox entry for offline account
activation, with a localized save-loss warning before writing
an account ID.
SettingPage hooks are process-wide, so stock pages such as PkgInstaller were being consumed by toolbox handlers. Track the active XML page, dispatch handlers by toolbox domain, pass stock pages through unchanged, and add host regression coverage.