fix(apple/tvOS): system-style slide for in-stack pushes (swiftui-navigation-transitions)

SwiftUI's NavigationStack on tvOS animates pushes as a bare crossfade with no public
customization — the system Settings app slides. The home stack now applies
.customNavigationTransition(.slide) on tvOS via davdroman/swiftui-navigation-transitions
(MIT, tvOS 13+), covering the top-level routes AND the settings pickers' drill-ins.

The dependency is referenced by the Xcode PROJECT only and linked solely by the
Punktfunk-tvOS target: its manifest (no macOS platform declared vs 10.15 deps) breaks
SwiftPM whole-graph validation for plain `swift build`, and the #if os(tvOS) import
never compiles in the macOS-only SwiftPM dev shell anyway. Headless builds need
xcodebuild -skipMacroValidation (the lib pulls Swift macro packages; in the Xcode UI
it's a one-time Trust & Enable prompt).

iOS/macOS keep their untouched system navigation animations.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Package.swift

@@ -24,6 +24,9 @@ let package = Package(
             ]
         ),
         // Development app shell (swift run PunktfunkClient): connect form → stream + input.
+        // (The tvOS slide-transition package is referenced by the Xcode PROJECT only —
+        // its manifest breaks SwiftPM whole-graph validation on macOS, and only the
+        // Punktfunk-tvOS target links it; the #if os(tvOS) import never compiles here.)
         .executableTarget(name: "PunktfunkClient", dependencies: ["PunktfunkKit"]),
         .testTarget(name: "PunktfunkKitTests", dependencies: ["PunktfunkKit"]),
     ]