Mega Man X2 v0.1.0 — SDL3 + first Linux build

What's new

First release with SDL3 and a Linux build.

• Ported to SDL3 (SDL2 remains available for local builds). Latest recomp-ui
  compiles its SDL3 backend unconditionally, so the previous hardcoded SDL2
  wiring no longer worked at all.
• First Linux AppImage for Mega Man X2. State — config.ini,
  keybinds.ini, rom.cfg, saves/, mods/ — lives next to the .AppImage,
  survives updates, and re-anchors if you move the file. Drop your ROM beside
  the .AppImage and it is picked up automatically.
• Windows archive now uses portable ZIP paths, so Linux and Steam Deck
  extractors rebuild the bundled assets/ and mods/packages/ hierarchy
  correctly. Previously a Proton user's extraction produced files literally named
  assets\fonts\... and the launcher found no fonts and no mods.
• Fixed a black screen under SDL3: SNES frames are opaque RGB with a zero alpha
  byte, which SDL3 blended away to the clear colour (audio kept playing).
• Production builds no longer announce a TCP debug server they do not have.

Notes

• A verified Mega Man X2 (USA) ROM is required and is not included.
• Windows: extract the full archive, then run MegaManX2SNESRecomp.exe. The
  bare .exe will not run without the bundled SDL3.dll, MinGW runtime DLLs and
  assets/.
• Linux: chmod +x the .AppImage and run it from a writable folder — that
  folder is where your config and saves live.
• Widescreen is a default-off option on the launcher's Mods page.