FieldScreen TV — Game fullscreen fix

The expand icon on a game pane now fills the display with that pane instead of switching to the 1 + 3 layout.

• Back to screens, Escape, or controller B restores the previous layout and audio focus.
• Channel order and player instances stay intact when entering and leaving fullscreen.
• The native app enters display fullscreen and restores its previous windowed/fullscreen state on return.
• The website demo uses the same corrected pane controls.

Validated with the existing 33 automated checks, a production build, package verification, and live-video fullscreen/return testing. Controller B follows the same exit action; physical Steam Deck controller testing was not performed.

Download the updated AppImage, or rerun the installer from the website. Saved providers remain available after updating.