perf(startup): let Windows relax the system timer resolution

On Windows SDL3 raises the global timer resolution with
timeBeginPeriod(1) and holds it for the whole process lifetime, which
keeps the system on a 1 ms tick and costs power for no benefit here.

- A startup hint now asks SDL to leave the system timer alone. Nothing
  in the app needs sub-15 ms waits: vsync paces drawing, the idle wait
  is 200 ms, and background sleeps are 50 ms or longer.

The hint is Windows-only in effect and is ignored elsewhere; an
environment override that turns it off is harmless.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main.cpp

@@ -2428,6 +2428,10 @@ int main(int argc, char* argv[])
 
 static bool InitSDL()
 {
+    // SDL3 otherwise holds timeBeginPeriod(1) for the process lifetime on Windows. Nothing here needs
+    // sub-15 ms waits (vsync pacing, the 200 ms idle wait, >=50 ms thread sleeps), so let the system
+    // timer relax. Ignored on non-Windows platforms; a false return (env override) is harmless.
+    SDL_SetHint(SDL_HINT_TIMER_RESOLUTION, "0");
     if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_GAMEPAD)) {
         fprintf(stderr, "Error: SDL_Init(): %s\n", SDL_GetError());
         return false;