On load, Cvars::reapply_saved_presets writes the saved graphicsQuality rung (and the saved
lightingQuality rung, else the Graphics rung's) over every governed row the file does not carry,
so a row registered after the save follows the preset instead of its registered default. Rows the
file carries and session-owned rows stay; Custom writes nothing. Tests for both ladders.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
