Keep the highlight slider off the greys, and start each mode clean

The highlight knee opened at 0.45, so dropping HIGHLIGHT pulled a mid-grey
down with the true highlights. It now opens at 0.65 (and the coefficient
drops 0.32 -> 0.22 to stay monotonic), so the slider leaves everything up to
a light grey untouched and still rolls the bright end off. Shadow is
untouched — its 0.00..0.55 knee was already right.

Switching between the library and the camera now drops the edits back to
the recipe's own values, no frame and no custom mark. A frame was picked
for the still it sat on and the mark was placed against that very photo, so
neither may follow the user across the switch (or into a live capture),
exactly like the sliders that were tuned on the photo in front of them.

src/dev/nativeBenchProbe.ts

@@ -53,7 +53,7 @@ export async function nativeBenchProbe(): Promise<void> {
     console.error('[BENCH] classic-neg-on-black matrix[0..4]=' + matrix.slice(0, 5).join(','));
 
     // P2 tone parity on solid ramps (expected values computed from TONE_SKSL):
-    //  white(255) hl=-1 -> 173; gray64 sh=+1 -> 113; white dr=1 -> 209;
+    //  white(255) hl=-1 -> 199; gray64 sh=+1 -> 113; white dr=1 -> 209;
     //  gray26 sh=+1 -> 105; gray26 hl=+1 sh=-1 -> 0.
     const toneGates: Array<{ rgb: [number, number, number]; tone: { dr: number; hl: number; sh: number }; tag: string }> = [
       { rgb: [255, 255, 255], tone: { dr: 0, hl: -1, sh: 0 }, tag: 'white-hl-1' },