fix: setup flow, connection page, and chat token bugs

[ranjeshj]

Summary

Fixes 12 bugs across setup flow, connection page, connection manager, and chat token resolution.

Wizard RadioButtons (user-reported)

• RadioButtons selection not sticking — \ConfigureRadioButtons\ always reassigned \ItemsSource\ on every re-render (even when items were identical), causing WinUI to reset the visual selection. Now skips \ItemsSource\ when items are content-equal.

ConnectionPage — Direct Connect

• SSH validation — empty user/host and invalid ports now rejected upfront before any state mutation
• Registry revert on failure — if connect fails, active gateway reverts to previous instead of leaving a broken config active
• Silent catches logged — identity file read/write errors now logged via \Debug.WriteLine\
• StateChanged leak — page now unsubscribes from \StateChanged\ on \Unloaded\

GatewayConnectionManager

• ReconnectAsync race condition — extracted \ConnectCoreAsync/\DisconnectCore\ so \ReconnectAsync\ and \SwitchGatewayAsync\ hold the semaphore atomically across disconnect+connect
• Deadlock risk — \DisposeActiveClient\ now uses \Task.Run\ to avoid sync context deadlocks
• Dispose timeout — tunnel stop in \Dispose()\ uses \Task.Run().Wait(3s)\ instead of unbounded \GetResult()\

Setup Flow

• Cancelled state persisted — cancellation now saves \Cancelled\ status before rethrowing, preventing stale \Running\ phase on restart
• Permanent failures classified — \UnauthorizedAccessException, \InvalidOperationException, etc. marked non-retryable
• Corrupt state file — \LoadAsync\ catches \JsonException, deletes corrupt file, starts fresh

Chat Token

• Wrong token for HTTP auth — \InteractiveGatewayCredentialResolver\ now prefers \SharedGatewayToken\ for chat/dashboard HTTP surfaces instead of \DeviceToken\ (which is for WebSocket auth)

Testing

• All 2353 tests pass (1443 shared + 910 tray)
• Manual testing: direct connect, chat, wizard radio buttons