feat: anti-slop design constraints + delete duplicate constants

Tightens design-consultation and design-shotgun to push back on the
convergence traps every AI design tool falls into.

Changes:
- scripts/resolvers/constants.ts: add "system-ui as primary font" to
  AI_SLOP_BLACKLIST. Document Space Grotesk as the new "safe alternative
  to Inter" convergence trap alongside the existing overused fonts.
- scripts/gen-skill-docs.ts: delete duplicate AI slop constants block
  (dead code — scripts/resolvers/constants.ts is the live source).
  Prevents drift between the two definitions.
- design-consultation/SKILL.md.tmpl: add Space Grotesk + system-ui to
  overused/slop lists. Add "anti-convergence directive" — vary across
  generations in the same project. Add Phase 1 "memorable-thing forcing
  question" (what's the one thing someone will remember?). Add Phase 5
  "would a human designer be embarrassed by this?" self-gate before
  presenting variants.
- design-shotgun/SKILL.md.tmpl: anti-convergence directive — each
  variant must use a different font, palette, and layout. If two
  variants look like siblings, one of them failed.

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

plan-design-review/SKILL.md

@@ -1211,6 +1211,7 @@ FIX TO 10: Rewrite vague UI descriptions with specific alternatives.
 8. Colored left-border on cards (`border-left: 3px solid <accent>`)
 9. Generic hero copy ("Welcome to [X]", "Unlock the power of...", "Your all-in-one solution for...")
 10. Cookie-cutter section rhythm (hero → 3 features → testimonials → pricing → CTA, every section same height)
+11. system-ui or `-apple-system` as the PRIMARY display/body font — the "I gave up on typography" signal. Pick a real typeface.
 
 Source: [OpenAI "Designing Delightful Frontends with GPT-5.4"](https://developers.openai.com/blog/designing-delightful-frontends-with-gpt-5-4) (Mar 2026) + gstack design methodology.
 - "Cards with icons" → what differentiates these from every SaaS template?