feat(store): Play feature graphic (1024x500) generator

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/ui/branding/feature_graphic_painter.dart

@@ -0,0 +1,36 @@
+// lib/ui/branding/feature_graphic_painter.dart
+import 'package:flutter/material.dart';
+
+import 'app_icon_painter.dart';
+
+/// Paints the Play feature graphic (1024×500): navy field, the brand blocks on
+/// the left, wordmark + tagline on the right.
+class FeatureGraphic {
+  static void paint(Canvas canvas, Size size) {
+    final rect = Offset.zero & size;
+    AppIconMark.paintBackground(canvas, rect);
+
+    // Blocks on the left, vertically centered.
+    canvas.save();
+    final blockArea = size.height * 0.74;
+    canvas.translate(size.height * 0.16, (size.height - blockArea) / 2);
+    AppIconMark.paintBlocks(canvas, blockArea, groupFraction: 0.92);
+    canvas.restore();
+
+    void text(String s, double dy, double fontSize, FontWeight w, Color c) {
+      final tp = TextPainter(
+        text: TextSpan(
+          text: s,
+          style: TextStyle(
+              color: c, fontSize: fontSize, fontWeight: w, letterSpacing: 0.5),
+        ),
+        textDirection: TextDirection.ltr,
+      )..layout();
+      tp.paint(canvas, Offset(size.height * 1.02, dy));
+    }
+
+    text('Block Seasons', size.height * 0.34, 76, FontWeight.w900, Colors.white);
+    text('A new season of blocks every few weeks.', size.height * 0.50, 30,
+        FontWeight.w500, const Color(0xFFB9C4E6));
+  }
+}

test/tool/generate_brand_assets_test.dart

@@ -3,6 +3,7 @@ import 'dart:io';
 import 'dart:ui';
 
 import 'package:block_seasons/ui/branding/app_icon_painter.dart';
+import 'package:block_seasons/ui/branding/feature_graphic_painter.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 Future<void> _writePng(String path, int size, void Function(Canvas) draw) async {
@@ -41,4 +42,20 @@ void main() {
       expect(File('assets/icon/$f').existsSync(), isTrue, reason: f);
     }
   });
+
+  testWidgets('generate feature graphic', (tester) async {
+    await tester.runAsync(() async {
+      const w = 1024, h = 500;
+      final recorder = PictureRecorder();
+      final canvas = Canvas(recorder);
+      FeatureGraphic.paint(canvas, const Size(1024, 500));
+      final picture = recorder.endRecording();
+      final image = await picture.toImage(w, h);
+      final bytes = await image.toByteData(format: ImageByteFormat.png);
+      File('docs/store/feature_graphic.png').parent.createSync(recursive: true);
+      File('docs/store/feature_graphic.png')
+          .writeAsBytesSync(bytes!.buffer.asUint8List());
+    });
+    expect(File('docs/store/feature_graphic.png').existsSync(), isTrue);
+  });
 }