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/s5-bottom-anchored.md

@@ -0,0 +1,13 @@
+### S5 · Bottom-anchored
+The label or heading sits *below* the section's content. Inverts hierarchy.
+*Use when:* the content is the primary act and the label is a footer to it.
+*Don't confuse with:* S1 Left-margin (which leads with the label).
+
+```html
+<section>
+  <div class="content">…</div>
+  <p class="num-label">— end of 02</p>
+</section>
+```
+
+---