photoshop_adjust_curves

Create a Curves adjustment layer on the active document. Users often say: make it pop, S-curve, fix flat image, auto tone, improve contrast. Use when: global tonal correction via a non-destructive Curves adjustment layer. Do NOT use when: stylistic cinematic grade — use photoshop_recipe_apply_color_grade. Returns: JSON { ok, summary, details: { layer_name, preset } }. Preconditions: active document. Side effects: adds Curves adjustment layer.