init: arcadia-admin — admin webapp for arcadia-core, cloned from vibespace

Initial commit. Spun up via the docs/STARTER.md recipe: cp from vibespace,
reset git, rename package, set brand to "Arcadia Admin" with Shield icon
in app/lib/identity.ts.

Inherits the full Crema sibling-lib wiring including @crema/arcadia-client
(typed HTTP + Phoenix Channels realtime against arcadia-core) and
@crema/arcadia-auth-ui (login/signup/password-reset/2FA forms). The /login
route already renders <LoginForm>; <ArcadiaProvider> in app/root.tsx reads
VITE_ARCADIA_URL (default localhost:4000) and VITE_ARCADIA_TENANT (default
"default").

CLAUDE.md and README rewritten to frame this as the admin app for
arcadia-core. docs/STARTER.md removed — arcadia-admin is a leaf consumer,
not a downstream starter.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/components/ui/radio-group.tsx

@@ -0,0 +1,36 @@
+import { Radio as RadioPrimitive } from "@base-ui/react/radio"
+import { RadioGroup as RadioGroupPrimitive } from "@base-ui/react/radio-group"
+
+import { cn } from "~/lib/utils"
+
+function RadioGroup({ className, ...props }: RadioGroupPrimitive.Props) {
+  return (
+    <RadioGroupPrimitive
+      data-slot="radio-group"
+      className={cn("grid w-full gap-2", className)}
+      {...props}
+    />
+  )
+}
+
+function RadioGroupItem({ className, ...props }: RadioPrimitive.Root.Props) {
+  return (
+    <RadioPrimitive.Root
+      data-slot="radio-group-item"
+      className={cn(
+        "group/radio-group-item peer relative flex aspect-square size-4 shrink-0 rounded-full border border-input outline-none after:absolute after:-inset-x-3 after:-inset-y-2 focus-visible:border-ring focus-visible:ring-3 focus-visible:ring-ring/50 disabled:cursor-not-allowed disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-3 aria-invalid:ring-destructive/20 aria-invalid:aria-checked:border-primary dark:bg-input/30 dark:aria-invalid:border-destructive/50 dark:aria-invalid:ring-destructive/40 data-checked:border-primary data-checked:bg-primary data-checked:text-primary-foreground dark:data-checked:bg-primary",
+        className
+      )}
+      {...props}
+    >
+      <RadioPrimitive.Indicator
+        data-slot="radio-group-indicator"
+        className="flex size-4 items-center justify-center"
+      >
+        <span className="absolute top-1/2 left-1/2 size-2 -translate-x-1/2 -translate-y-1/2 rounded-full bg-primary-foreground" />
+      </RadioPrimitive.Indicator>
+    </RadioPrimitive.Root>
+  )
+}
+
+export { RadioGroup, RadioGroupItem }