Accordion

# Aster Component Implementation Prompt — Accordion

## 1. Component Purpose & Canonical Role
- **Component:** Accordion (`accordion`)
- **Category:** Navigation & Layout
- **Native Element:** `<h3> + <button aria-expanded>`
- **Summary:** Stacked sections that open and close, so people can skip what they don't need.
- **When to Use:** FAQs, configuration groups, and collapsible architecture details.
- **When Not to Use:** Content that users must read all at once.

## 2. Authoritative Repository Files
- **Component CSS:** `components/accordion/accordion.css`
- **Component Spec:** `docs/components/accordion.md`
- **Agent Contract:** `skills/using-aster-components/SKILL.md`
- **Compiled Bundle:** `dist/css/aster.css` and `dist/js/aster.js`

## 3. Canonical HTML Structure & Classes
```html
<div class="as-accordion" data-single="true">
  <div class="as-accordion__item">
    <h3 class="as-accordion__heading">
      <button type="button" class="as-accordion__trigger" aria-expanded="true" aria-controls="sec-1" id="trig-1">
        <span class="as-accordion__title">Zero-Downtime Rollout Strategy</span>
        <svg class="as-accordion__chevron" viewBox="0 0 16 16" aria-hidden="true"><polyline points="4 6 8 10 12 6"/></svg>
      </button>
    </h3>
    <div class="as-accordion__panel" id="sec-1" role="region" aria-labelledby="trig-1">
      <div class="as-accordion__content">Pods are drained gracefully...</div>
    </div>
  </div>
</div>
```

## 4. Measured Geometry
Measured from the rendered component when this page loads.

## 5. Non-Negotiable Aster Constraints
1. **Zero Primitive Color Leaks:** Bind colors strictly to `--as-semantic-color-*` custom properties. Never use `--as-color-primitive-*` or hardcoded hex values in component usage.
2. **Minimum 4px Radius Policy:** Never use `2px` border-radius. Use `--as-radius-sm` (`4px`), `--as-radius-md` (`8px`), `--as-radius-lg` (`12px`), or `--as-radius-full` (`9999px`).
3. **Single Standard Density Mode:** Compact mode (`data-density="compact"` / `.as-*--compact`) is permanently retired. Do not emit compact classes or attributes.
4. **WCAG 2.2 AA Accessibility:** Maintain >= 4.5:1 text contrast, >= 3:1 UI/border contrast, >= 24x24px interactive hit targets, and full keyboard operability (`Tab`, `Enter`, `Space`, `Escape`, Arrow keys).

## 6. Verification Commands
```bash
npm run test:components
npm run test:contrast
npm run test:browser
```