A probe window opens unfocused and WinitSettings::game() drives an unfocused
window at reactive 1/60 s, so every FPS_PROBE read ~16.7 ms whatever the scene
cost (Classic at 720p with 0.4 ms of GPU read 57 fps). Probes now run
Continuous in both modes. Adds perf-northshire-night / perf-abbey-night.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>