添加 hallmark 技能

skills/hallmark/references/components/n3-side-rail.md

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+### N3 · Side-rail
+A thin vertical strip on the left edge — wordmark rotated, plus 2–3 dot-indicators for sections. Editorial / portfolio energy.
+*Use when:* the page is long and section-numbered.
+*Don't confuse with:* N1 Top wordmark (which is horizontal).
+
+```html
+<nav class="nav-rail">
+  <p class="wordmark vertical">Studio</p>
+  <ul class="dots"><li></li><li></li><li></li></ul>
+</nav>
+```
+```css
+.nav-rail { position: fixed; left: 0; top: 0; bottom: 0; width: 3rem; padding: var(--space-md); writing-mode: vertical-rl; }
+```