feat: nuevos componentes UI — accordion, avatar, breadcrumb, checkbox, command, dropdown, pagination, popover, radio, sheet, select, switch, textarea, toast

Componentes React accesibles basados en Radix UI con soporte de temas via CSS variables. Incluye barrel export en index.ts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/functions/ui/breadcrumb.md

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+---
+name: breadcrumb
+kind: component
+lang: ts
+domain: ui
+version: "1.0.0"
+purity: impure
+signature: "Breadcrumb(props: BreadcrumbProps): JSX.Element"
+description: "Navegacion jerarquica con separadores, elipsis para paths largos y soporte para router links via asChild."
+tags: [breadcrumb, navigation, component, ui]
+uses_functions: [cn_ts_core]
+uses_types: []
+returns: []
+returns_optional: false
+error_type: ""
+imports: ["lucide-react"]
+tested: false
+tests: []
+test_file_path: ""
+file_path: "frontend/functions/ui/breadcrumb.tsx"
+props:
+  - name: className
+    type: "string"
+    required: false
+    description: "Clases CSS adicionales"
+emits: []
+has_state: false
+framework: react
+variant: []
+---
+
+## Ejemplo
+
+```tsx
+<Breadcrumb>
+  <BreadcrumbList>
+    <BreadcrumbItem>
+      <BreadcrumbLink href="/">Inicio</BreadcrumbLink>
+    </BreadcrumbItem>
+    <BreadcrumbSeparator />
+    <BreadcrumbItem>
+      <BreadcrumbLink href="/docs">Documentacion</BreadcrumbLink>
+    </BreadcrumbItem>
+    <BreadcrumbSeparator />
+    <BreadcrumbItem>
+      <BreadcrumbPage>Componentes</BreadcrumbPage>
+    </BreadcrumbItem>
+  </BreadcrumbList>
+</Breadcrumb>
+
+// Con elipsis para paths largos
+<Breadcrumb>
+  <BreadcrumbList>
+    <BreadcrumbItem>
+      <BreadcrumbLink href="/">Inicio</BreadcrumbLink>
+    </BreadcrumbItem>
+    <BreadcrumbSeparator />
+    <BreadcrumbItem>
+      <BreadcrumbEllipsis />
+    </BreadcrumbItem>
+    <BreadcrumbSeparator />
+    <BreadcrumbItem>
+      <BreadcrumbPage>Pagina actual</BreadcrumbPage>
+    </BreadcrumbItem>
+  </BreadcrumbList>
+</Breadcrumb>
+```
+
+## Notas
+
+Exports: Breadcrumb (nav), BreadcrumbList (ol), BreadcrumbItem (li), BreadcrumbLink (a con asChild), BreadcrumbPage (span aria-current=page), BreadcrumbSeparator (ChevronRight por defecto, customizable), BreadcrumbEllipsis (MoreHorizontal). BreadcrumbLink acepta asChild para usar con Link de React Router o Next.js.