feat: add privileged same-origin plugin tier + crypto API surface

app/(sandbox)/plugin-sandbox-privileged/page.tsx

@@ -0,0 +1,15 @@
+import { SandboxRuntime } from '@/lib/plugin-sandbox/runtime';
+
+// Privileged-tier sandbox route. Identical runtime to /plugin-sandbox, but the
+// host loads it into a same-origin (`allow-same-origin`) iframe so the bundle
+// gets real `crypto.subtle` + IndexedDB. The trust gate (signature + admin
+// approval) is enforced host-side before this route is ever framed; the page
+// itself carries no extra privilege.
+//
+// Must be dynamic so the per-request CSP nonce from proxy.ts is embedded in
+// Next's injected hydration/chunk scripts.
+export const dynamic = 'force-dynamic';
+
+export default function PrivilegedPluginSandboxPage() {
+  return <SandboxRuntime />;
+}