chore(studio): RadioGroup migration + second integration test

Two clean-ups:

- `fai_system_ai_editor.dart` uses the new `RadioGroup<T>`
  ancestor pattern Material 3 introduced after Flutter 3.32.
  Same UX (three radios for off/redacted/full), no
  deprecation warnings, `flutter analyze` is now zero-issue
  for the whole project.
- New `install_install_planned_test.dart` asserts that
  installing a `planned` seed entry surfaces a clear,
  human-readable error class (no panic, no silent success).
  Locks in the failed-precondition path Studio's
  friendly-error mapper depends on.

Integration test suite is now 3 scenarios:
  - capabilities_test.dart: system.approval+kind tag
  - install_install_planned_test.dart: planned-install error

All run against a fresh `fai serve` subprocess via
HubFixture, ~2 s total.

Signed-off-by: flemming-it <sf@flemming.it>
Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

test/integration/install_install_planned_test.dart

@@ -0,0 +1,42 @@
+// Integration test: install_module against a `planned` seed
+// entry must fail with a clear, human-readable error class —
+// not a panic, not a silent success.
+//
+// Why this matters: planned modules are listed in the Store
+// but have no wasm_url. The old behaviour was a server-side
+// panic on resolve_install_source(); the new contract emits a
+// FAILED_PRECONDITION with "no installable version" so
+// Studio's friendly-error mapper can show a usable message.
+
+import 'package:flutter_test/flutter_test.dart';
+
+import 'hub_fixture.dart';
+
+void main() {
+  test('install_module on a planned entry surfaces a clear error',
+      () async {
+    final fixture = await HubFixture.start();
+    if (fixture == null) return;
+    try {
+      // web.scrape is `planned` in the seed and has no
+      // wasm_url. The hub resolves the name through the store
+      // index, finds the entry, then fails at the
+      // "no installable version" check.
+      try {
+        await fixture.client.installModule(source: 'web.scrape');
+        fail('install_module should not succeed for a planned entry');
+      } catch (e) {
+        final msg = e.toString();
+        expect(
+          msg.contains('no installable version') ||
+              msg.contains('not yet published'),
+          isTrue,
+          reason:
+              'Expected a clear planned-status error, got: $msg',
+        );
+      }
+    } finally {
+      await fixture.dispose();
+    }
+  });
+}