fix(tizen): drop the fullscreen toggle from the TV sidebar

[balcsida]

What

_showFullscreenToggle was gated on Platform.isWindows || Platform.isLinux. Tizen reports itself as Linux through dart:io, so the fullscreen button was still rendering on the TV sidebar — at all four of its sites (side_navigation_rail.dart:685, :779, :1100, plus the nav-key list).

- bool get _showFullscreenToggle => Platform.isWindows || Platform.isLinux;
+ bool get _showFullscreenToggle => PlatformDetector.isDesktopOS() && !Platform.isMacOS;

A TV has no windowed surface to toggle, and window_manager has no Tizen implementation, so the button could only ever fail.

Why this shape

This branch already routes the Tizen form factor through PlatformDetector.isDesktopOS(), which excludes Tizen. Asking the same gate here keeps the decision in one place instead of adding a third platform literal — any future platform that is a TV-but-reports-desktop is then handled once. The !Platform.isMacOS term preserves the existing intent recorded in the doc comment: macOS has the system green button, so it never wanted this toggle either.

Behaviour on every other platform is unchanged: isDesktopOS() is Windows || macOS || Linux, minus macOS, which is exactly the original Windows || Linux.

Verification

• flutter analyze lib/widgets/side_navigation_rail.dart — clean
• flutter test test/widgets/side_navigation_rail_test.dart — 20/20 pass
• dart format --page-width 120 applied

Not verified on real hardware — I have no Tizen device. The change is a pure compile-time gate, so the risk is confined to whether TIZEN_BUILD is defined for the build, which this branch already handles.

Credit

The Tizen platform-detection approach this builds on comes from edde746#1164 by @George-Fam, who ported the app to Tizen against real hardware (Samsung QN43LS01B, Tizen 10) — including a custom C#/Capi player backend and the Wayland focus fix for remote key delivery. This is a one-line gap in that groundwork, not a new idea.

AI assistance

Written with Claude Opus 5 via Claude Code, per CONTRIBUTING.md.

🤖 Generated with Claude Code