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/s4-inline-no-break.md

@@ -0,0 +1,11 @@
+### S4 · Inline (no break)
+The heading is a small caps phrase that emerges *inside* the body flow; no spatial break.
+*Use when:* the page is prose-led; reading should be continuous.
+*Don't confuse with:* S2 Hanging (which separates with negative space).
+
+```html
+<p>… <span class="head-inline">A small heading.</span> …</p>
+```
+```css
+.head-inline { font-variant-caps: all-small-caps; letter-spacing: 0.06em; font-weight: 500; }
+```