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>

scripts/resolvers/constants.ts

@@ -1,6 +1,13 @@
 // ─── Shared Design Constants ────────────────────────────────
 
-/** gstack's 10 AI slop anti-patterns — shared between DESIGN_METHODOLOGY and DESIGN_HARD_RULES */
+/**
+ * gstack's AI slop anti-patterns — shared between DESIGN_METHODOLOGY and DESIGN_HARD_RULES.
+ *
+ * Overused fonts worth calling out in templates (not a pattern to blacklist, but a
+ * convergence risk): Inter, Roboto, Arial, Helvetica, Open Sans, Lato, Montserrat,
+ * Poppins, and increasingly Space Grotesk. Every AI design tool picks one of these.
+ * Design prompts should bias toward less-common display faces.
+ */
 export const AI_SLOP_BLACKLIST = [
   'Purple/violet/indigo gradient backgrounds or blue-to-purple color schemes',
   '**The 3-column feature grid:** icon-in-colored-circle + bold title + 2-line description, repeated 3x symmetrically. THE most recognizable AI layout.',
@@ -12,6 +19,7 @@ export const AI_SLOP_BLACKLIST = [
   'Colored left-border on cards (`border-left: 3px solid <accent>`)',
   'Generic hero copy ("Welcome to [X]", "Unlock the power of...", "Your all-in-one solution for...")',
   'Cookie-cutter section rhythm (hero → 3 features → testimonials → pricing → CTA, every section same height)',
+  'system-ui or `-apple-system` as the PRIMARY display/body font — the "I gave up on typography" signal. Pick a real typeface.',
 ];
 
 /** OpenAI hard rejection criteria (from "Designing Delightful Frontends with GPT-5.4", Mar 2026) */