Alpha 2c: Fullscreen, Not Full Stop

A small maintenance update for Windows and Linux. Same game, fewer window dramas.

• Fixes a reproduced crash when minimizing or restoring the game around
  fullscreen transitions: the runtime now waits for a valid graphics frame
  instead of submitting to an unavailable window surface.
• Keeps window events responsive while the display surface is being recreated,
  without advancing game time during the pause.
• Adds repeatable checks for fullscreen/windowed transitions, resolution changes
  and automatic rollback of unconfirmed settings.

USA/EUR ROM support, Forge's bundled shader preparation, TopScreen and save
formats are unchanged. No title recompilation or SDK is needed.

Back up your saves and settings before updating. Windows users should extract
the ZIP into a fresh folder and keep their previous installation until the new
one is working. Linux users can install the Flatpak over the previous version;
application data remains outside the package.

This fixes a concrete reproduced failure, not every possible driver or fullscreen
issue. Physical Steam Deck testing and unrelated Windows loader investigations
remain outstanding.

Thanks to Sion (@999sian) for the Linux, compatibility, cache and TopScreen
contributions retained from alpha.2; individual PR credits.
And to rlgcarrot for the TopScreen design reimplemented here, plus Azahar,
Ship of Harkinian, libultraship and NRI for the foundations.