feat: add Base UI Tailwind component library

Add composable wrappers for 37 Base UI component families.

Expose primitive and convenience APIs with shared styling utilities.

Add the registry manifest, installer CLI, generation and export checks.

Include a smoke example covering primitive and shadcn-style imports.

src/components/ui/checkbox/root.tsx

@@ -0,0 +1,26 @@
+"use client"
+
+import * as React from "react"
+import { Checkbox as BaseCheckbox } from "@base-ui/react/checkbox"
+import { cn } from "@/lib/utils"
+
+export type CheckboxRootProps = React.ComponentPropsWithoutRef<typeof BaseCheckbox.Root> & {
+  className?: string
+}
+
+const BaseCheckboxRoot = BaseCheckbox.Root as React.ElementType
+
+export const CheckboxRoot = React.forwardRef<HTMLElement, CheckboxRootProps>(
+  ({ className, ...props }, ref) => (
+    <BaseCheckboxRoot
+      ref={ref}
+      className={cn(
+        "flex size-4 shrink-0 items-center justify-center rounded-none border border-neutral-950 bg-white p-0 text-white data-checked:bg-neutral-950 data-checked:text-white focus-visible:outline-2 focus-visible:outline-solid focus-visible:outline-offset-2 focus-visible:outline-neutral-950 dark:border-white dark:bg-neutral-950 dark:text-neutral-950 dark:data-checked:bg-white dark:data-checked:text-neutral-950 dark:focus-visible:outline-white",
+        className,
+      )}
+      {...props}
+    />
+  ),
+)
+
+CheckboxRoot.displayName = "CheckboxRoot"