* feat(perf-probe): add FPS overlay toggle and tidy probe modal
Add optional rAF-based FPS readout controlled by a persisted probe flag.
Remove the separate keyboard shortcut. Collapse all phase sections by default.
* perf(fps-overlay): subscribe only to showFpsOverlay flag
Add usePerfProbeFlag so the overlay does not re-render when other probe
toggles change. Track the animation frame id with a loop-local variable.
cucadmuh