skill: restore prescriptive cream/sand/beige paragraph

Bisection across 5 historical skill commits on Gemini 3.5 flash fast
lane n=3 found that 0cf2debd was the peak quality state. The regression
between 0cf2debd and HEAD came from simplifying the long anti-cream
paragraph into a one-liner.

Restoring the paragraph (with em-dashes replaced by parens to satisfy
prose lint) recovers ~0.22pt average on Gemini vs HEAD, with the
largest gains on:
- 09-luxury-hotel: +0.50 (restores editorial drama in photo-led briefs)
- 10-food-magazine: +0.67
- 03-italian-restaurant: +0.51

The paragraph's load-bearing parts are the (a)(b)(c) alternatives that
give the model actionable replacements for cream-tinted body bg
("saturated brand color as body", "true off-white at chroma 0",
"darker mid-tone tinted neutral"). Without them, the one-line warning
left the model with no concrete alternative.

Cross-provider validation showed the pattern matches historical
behavior: Gemini benefits from prescriptive scaffold (+0.12 over off),
Sonnet is roughly neutral (+0.01), GPT-5.5 slightly regresses (-0.11
matching the v3.1.0 pattern of -0.11). The skill has never been
uniformly better than skill-off across providers; this is the closest
achievable state without provider-specific rework.

The structural improvements from the prior restructure stay (file
merges, S-tier inlines, routing rule extension, reveal-animation
safety rule).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

skill/SKILL.md

@@ -92,7 +92,7 @@ Two hard typographic ceilings you currently miss:
 #### Color & Theme
 
 - Use OKLCH.
-- Don't default to a cream / sand / beige body bg (white is fine) - this is a common AI trope in 2026.
+- **The cream / sand / beige body bg is the saturated AI default of 2026.** The whole warm-neutral band (OKLCH L 0.84-0.97, C < 0.06, hue 40-100) reads as cream/sand/paper/parchment regardless of what you call it. Token names like `--paper`, `--cream`, `--sand`, `--bone`, `--flour`, `--linen`, `--parchment`, `--wheat`, `--biscuit`, `--ivory` are tells in themselves. If the brief is "warm, traditional, family-coastal-Italian" or "magazine-warm" or "editorial-restraint", DO NOT translate that into a near-white warm-tinted bg; that's the AI move. Pick: (a) a saturated brand color as the body (terracotta, oxblood, deep ochre, near-black), (b) a true off-white at chroma 0 (or chroma toward the brand's own hue, not toward warmth-by-default), or (c) a darker mid-tone tinted neutral that's clearly the brand's own. "Warmth" in the brand is carried by accent + typography + imagery, not by body bg.
 - Tinted neutrals: add 0.005–0.015 chroma toward the brand's hue. Don't default-tint toward warm or cool "because the brand feels that way"; that's the cross-project monoculture move.
 - When picking a theme: Dark vs. light is never a default. Not dark "because tools look cool dark." Not light "to be safe.".Before choosing, write one sentence of physical scene: who uses this, where, under what ambient light, in what mood. If the sentence doesn't force the answer, it's not concrete enough. Add detail until it does.
 - Pick a **color strategy** before picking colors. Four steps on the commitment axis: