Add Accordion, Textarea, Select, and Card components; fix Input focus shift

New components:
- Accordion: compound component with single/multiple mode, grid-rows animation
- Textarea: multi-line input with auto-resize, character count, outlined/stacked variants
- Select: custom dropdown with keyboard navigation, combobox/listbox ARIA pattern
- Card: 4 variants (surface/outlined/elevated/filled) with header action support

Changes:
- Fix Input/Textarea focus ring layout shift (ring-1 instead of border-2)
- Add small/xsmall sizes to IconButton for card action contexts
- Add --radius-xl token (16px) for larger container corners

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/tokens/tokens.css

@@ -115,6 +115,7 @@
   --radius-sm: 4px;
   --radius-default: 6px;
   --radius-lg: 10px;
+  --radius-xl: 16px;
   --radius-full: 9999px;
 
   /* Shadows */