Dev
d4fe169bd8
feat(06-01): extend FeatureViewModelBase with GlobalSites support
- Add protected GlobalSites property (IReadOnlyList<SiteInfo>) initialized to Array.Empty
- Register GlobalSitesChangedMessage in OnActivated alongside TenantSwitchedMessage
- Add private OnGlobalSitesReceived to update GlobalSites and invoke virtual hook
- Add protected virtual OnGlobalSitesChanged for derived VMs to override
- [Rule 3 - Blocking] Fix MainWindowViewModel missing ExecuteOpenGlobalSitePicker and BroadcastGlobalSites stubs referenced in constructor (pre-existing partial state from earlier TODO commit)