gr.flashScreen() adds its color to every pixel after tonemapping, so
during a strong flash any bright effect on screen clips to white. The
MediaVPs blinding effect does this for several seconds after big
explosions, flattening impact flashes into featureless white discs.
flashScreenAlpha() blends the screen toward the color instead, using the
existing gr_flash_alpha() path. Over a black background the result is
the same as flashScreen, but bright pixels keep their detail. Also
describe what flashScreen actually does in its help text.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
