feat(pills): ON-AIR armable signed-out; Start face reads Sign-In while armed signed-out (Good Dog 2026-09-20 ruling, ai.md updated same commit)

ViewModels/MainViewModel.Account.cs

@@ -20,7 +20,7 @@ public partial class MainViewModel
                 // ON-AIR requires a sign-in; dropping the session turns the pill
                 // off so the state can never offer a stream without an account.
                 if (!value) OnAirPillOn = false;
-                OnPropertyChanged(nameof(CanToggleOnAir));
+                OnPropertyChanged(nameof(PrimaryStartButtonLabel));
                 OnPropertyChanged(nameof(ShowPrimaryStartButton));
                 OnPropertyChanged(nameof(AccountStatusLightToolTip));
             }
@@ -45,7 +45,7 @@ public partial class MainViewModel
     public string AccountStatusLightToolTip =>
         IsLive ? "Live on YouTube — the top bar is red to show the stream is on the air."
         : IsConnected ? "You're signed in to YouTube. The light is green; ON-AIR is available."
-        : "Signed out — the light is red and the ON-AIR pill is greyed out. You can still record locally.";
+        : "Signed out — the light is red. You can still record locally; arming ON-AIR arms intent, and Start turns that intent into a sign-in.";
 
     // Restores the DPAPI-saved OAuth session so sign-in survives restarts.
     // Best-effort: refresh a near-expiry access token; a session that can no