fix(mobile): clip preset agent avatar previews to the squircle

Catalog avatars in the picker and Create agent previews rendered unclipped,
so the default create preview did not match the created agent. Let
PresetAgentAvatar own the agent clip and assert the catalog state in the
picker journey.

Co-authored-by: studio <dc2fc481343672df31a689840c09299972e704dac592e0da6f18486646a7ee3e@localhost>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tom Brow <tomb@squareup.com>

mobile/lib/shared/widgets/preset_agent_avatar.dart

@@ -7,6 +7,7 @@ import 'package:video_player/video_player.dart';
 
 import '../animated_avatar.dart';
 import 'avatar_image.dart';
+import 'avatar_shape.dart';
 import 'android_transparent_avatar.dart';
 
 /// Plays the transparent video paired with a bundled character poster.
@@ -98,6 +99,8 @@ class PresetAgentAvatar extends HookWidget {
 
     return SizedBox.square(
       dimension: size,
+      child: AvatarClip(
+        isAgent: true,
         child: Transform.scale(
           scale: animatedAvatarArtworkScale,
           child: isAndroid && videoUrl != null
@@ -114,6 +117,7 @@ class PresetAgentAvatar extends HookWidget {
               ? VideoPlayer(controller)
               : AvatarImageContent(imageUrl: poster, fallback: fallback),
         ),
+      ),
     );
   }
 }

mobile/test/features/agents/agent_avatar_picker_test.dart

@@ -67,17 +67,8 @@ void main() {
     await tester.pumpAndSettle();
     expect(selection.url, isNot(agentAvatarCatalog.first.url));
     final character = selection.url;
-    await tester.runAsync(() async {
+    // Every preview uses the same squircle the agent gets once created.
-      rendered = Completer<void>();
+    void expectSquirclePreview() {
-      tester
-          .widget<SegmentedButton<int>>(find.byType(SegmentedButton<int>))
-          .onSelectionChanged!({1});
-      await rendered.future.timeout(const Duration(seconds: 5));
-    });
-
-    await tester.pumpAndSettle();
-    expect(selection.bytes, isNotNull);
-    // The preview uses the same squircle the agent gets once created.
       final previewClip = tester.widget<ClipPath>(
         find.descendant(
           of: find.bySemanticsLabel('Selected agent avatar'),
@@ -88,6 +79,20 @@ void main() {
         (previewClip.clipper! as ShapeBorderClipper).shape,
         avatarShape(isAgent: true),
       );
+    }
+
+    expectSquirclePreview();
+    await tester.runAsync(() async {
+      rendered = Completer<void>();
+      tester
+          .widget<SegmentedButton<int>>(find.byType(SegmentedButton<int>))
+          .onSelectionChanged!({1});
+      await rendered.future.timeout(const Duration(seconds: 5));
+    });
+
+    await tester.pumpAndSettle();
+    expect(selection.bytes, isNotNull);
+    expectSquirclePreview();
     expect(
       (tester
                   .widget<GridView>(