Steam Deck: first-run preset (native 1280x800 fullscreen, MSAA 4, 150% draw/LOD distance) (#77)

STEAMOS detection in main() seeds video config defaults before configLoad;
first-launch-only by construction (an existing ge007.ini always wins). The
150% DrawDistance/LodDistance addresses authored N64 fade distances reading
short on the close-up Deck panel (e.g. the Dam lock fading in within sight)
while desktops keep the faithful 100% default.

README.md

@@ -98,7 +98,10 @@ The Linux bundle is the Deck build. SFTP it over from your PC, or download
 it straight from the [releases page](../../releases) on the Deck itself:
 unzip, drop your ROM in `data/`, run `prepare-assets` once, and add the
 executable as a non-Steam game. SDL2 is bundled, so no dependencies need
-installing. The renderer is CPU-bound (software RSP); expect original N64-era
+installing. On SteamOS the first launch seeds `ge007.ini` with Deck-friendly
+defaults — native 1280×800 fullscreen, VSync, MSAA 4, and 150% draw/LOD
+distance (the authored N64 fade distances read short on the close-up panel);
+everything is changeable in the options overlay and persists afterwards. The renderer is CPU-bound (software RSP); expect original N64-era
 performance at 60 fps rather than more. A v0.1.0-era crash on the Deck in
 Facility was never reproduced and its prime suspect has since been fixed, but
 this release has not yet been verified on real Deck hardware.