feat: add hallmark design skill

Anti-AI-slop design skill (greenfield pages, audits, redesigns, design
extraction from URLs/screenshots) -- installed and validated in an
earlier session, was sitting untracked. Full reference library:
components, macrostructures, themes, genres, verbs (audit/redesign).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

skills/hallmark/references/components/f1-bento-grid.md

@@ -0,0 +1,20 @@
+
+### F1 · Bento grid
+Asymmetric grid of 8–15 tiles in mixed spans (1×1, 2×1, 1×2, 2×2). Visual rhythm via size.
+*Use when:* multiple equally-valid entry points; SaaS feature page.
+*Don't confuse with:* F2 Sticky-scroll (which stacks vertically with sticky pacing).
+
+```html
+<section class="bento">
+  <article class="cell span-2x2">…</article>
+  <article class="cell span-1x1">…</article>
+  <article class="cell span-2x1">…</article>
+</section>
+```
+```css
+.bento { display: grid; grid-template-columns: repeat(4, 1fr); grid-auto-rows: 12rem; gap: var(--space-md); }
+.span-2x2 { grid-column: span 2; grid-row: span 2; }
+.span-2x1 { grid-column: span 2; }
+.span-1x2 { grid-row: span 2; }
+@media (max-width: 56rem) { .bento { grid-template-columns: repeat(2, 1fr); } }
+```