feat: Implement ASCII theme cycling and add quadrant theme support

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_dart/test/rendering/ascii_themes_test.dart

@@ -0,0 +1,20 @@
+import 'package:test/test.dart';
+import 'package:wolf_3d_dart/wolf_3d_renderer.dart';
+
+void main() {
+  group('AsciiThemes', () {
+    test('contains quadrant as a selectable style', () {
+      expect(AsciiThemes.values, contains(AsciiThemes.quadrant));
+    });
+
+    test('cycles through blocks and quadrant', () {
+      expect(AsciiThemes.nextOf(AsciiThemes.blocks), AsciiThemes.quadrant);
+      expect(AsciiThemes.nextOf(AsciiThemes.quadrant), AsciiThemes.blocks);
+    });
+
+    test('defaults to first style when unknown style is provided', () {
+      const custom = AsciiTheme('Custom', 'Xx ');
+      expect(AsciiThemes.nextOf(custom), AsciiThemes.blocks);
+    });
+  });
+}