Frequency-separation skin smoothing (Smoothing / Texture / Scale, global + per-mask)

[SandeepSubba]

Description

Adds a beauty-retouch toolset to the Details section — globally and inside mask adjustments, so the intended workflow is: AI-subject/brush mask over skin (subtract eyes/lips), then dial in:

• Skin Smoothing (0–100) — flattens the tonal-blotch band, with an edge guard that fades the effect where normalized mid-band contrast is high (eyes, brows, lips, hair boundaries keep their acutance)
• Skin Texture (0–100, neutral 50) — how much pore-scale detail is re-injected: 0 = classic soft-glamour blur, 100 = near-original texture with tone-evening only
• Smoothing Scale (0–100) — the frequency-separation point: blends the flatten base from the clarity blur (~8px, micro-blotches) toward the structure blur (~40px, large patches like under-eye shadows and redness)

Why not negative clarity?

Negative clarity mixes toward the blurred copy, killing pores and hair along with the blotches — the "plastic skin" look. This is proper frequency separation built on the blur pyramid the shader already binds:

fine  = color − tonal_blur                     (pores, hair — preserved)
base  = mix(clarity_blur, structure_blur, s)   (separation point)
out   = mix(color, base, a·edge_guard) + fine · a · tex

Engineering notes

• No new blur passes — all bands used (tonal/clarity/structure) were already computed and bound
• No GPU uniform layout changes — the three fields consume existing pad slots in GlobalAdjustments and MaskAdjustments (WGSL + Rust kept in lockstep)
• Per-mask accumulation follows the clarity/structure pattern; texture accumulates as deviation-from-neutral so untouched masks contribute nothing
• Old sidecars unaffected — missing keys parse to neutral values, not zero

Type of Change

• Bug fix
• New feature

Testing

• I have tested these changes locally and confirmed that they work as expected without issues

Verified with scripted A/B renders of portrait raws through the full GPU pipeline: at smoothing 80, texture 50 keeps pores while flattening blotches; texture 100 retains near-original texture density; scale 100 evens large tonal patches with eyes crisp. cargo check and tsc clean on this base.

AI Disclosure

• This PR is AI-generated but guided by a human

🤖 Generated with Claude Code