Remove supra brand from design system

Supra (VivoKey MD3 theme) has been extracted into a standalone
Dangerous-Pi theme plugin. Remove all supra references from tokens,
web CSS, showcase apps, and documentation.

- Delete supra brand tokens and elevation.css
- Update ThemeBrand type to "dt" | "classic"
- Remove supra from CSS generation, imports, and bevels
- Update CLAUDE.md and package READMEs

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

packages/web/src/components/bevels.css

@@ -126,7 +126,7 @@
 }
 
 [data-brand="dt"] .btn-secondary:hover::before {
-  background: rgba(var(--color-primary-rgb), 0.1);
+  background: var(--color-surface-hover);
 }
 
 /* ============================================================================
@@ -187,6 +187,18 @@
   --badge-fill: rgba(var(--color-info-rgb), 0.25);
 }
 
+/* ============================================================================
+   Badge text override for Classic — ensure readable text in light mode
+   Status-color text on 25% opacity backgrounds fails WCAG AA on light bg.
+   Use primary text color instead (same approach as DT badges above).
+   ============================================================================ */
+[data-brand="classic"] .badge-success,
+[data-brand="classic"] .badge-error,
+[data-brand="classic"] .badge-warning,
+[data-brand="classic"] .badge-info {
+  color: var(--color-text-primary);
+}
+
 /* ============================================================================
    Opt-in Bevel Utility Classes
    Use these for custom elements that need bevel shapes