Drop the mainnet/testnet/regtest ComboBox from the wizard and fix Net to always return NetKind.Mainnet. Core profiles and CLI --net flag are untouched; the wallet file still records the network name.
1300-line monolith → 7 focused files (max 359 lines each): MainWindowViewModel.cs core fields, constructor, lifecycle MainWindowViewModel.Wizard.cs setup wizard and wallet open/close flows MainWindowViewModel.Settings.cs language, unit, overlay flags MainWindowViewModel.Sync.cs server config, connection, sync loop MainWindowViewModel.Send.cs send panel MainWindowViewModel.Contacts.cs contact management MainWindowViewModel.Receive.cs balance display, QR, addresses, tx details No behaviour change, no XAML change, 127/127 tests pass.
davide