Refactor theme implementation to use ColorScheme.fromSeed for light and dark themes; update README with usage examples and add widgetbook build configuration.

README.md

@@ -33,6 +33,85 @@ flutter run
 
 See `melos.yaml`, `analysis_options.yaml`, and the package-level READMEs.
 
+## Using the M3E Theme
+
+The design tokens and helpers live in the `m3e_design` package. Import it once in files where you access the theme:
+
+```dart
+import 'package:m3e_design/m3e_design.dart';
+```
+
+- Install the theme once at the app level (one-liner):
+
+```dart
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      theme: ColorScheme.fromSeed(seedColor: Colors.teal).toM3EThemeData(),
+      home: const MyHomePage(),
+    );
+  }
+}
+```
+
+- With dynamic color (Android 12+), setting both light and dark themes:
+
+```dart
+Widget buildDynamicApp() {
+  return DynamicColorBuilder(
+    builder: (lightDynamic, darkDynamic) {
+      final light = lightDynamic ?? ColorScheme.fromSeed(seedColor: Colors.teal);
+      final dark = darkDynamic ??
+          ColorScheme.fromSeed(seedColor: Colors.teal, brightness: Brightness.dark);
+      return MaterialApp(
+        theme: light.toM3EThemeData(),
+        darkTheme: dark.toM3EThemeData(),
+        home: const MyHomePage(),
+      );
+    },
+  );
+}
+```
+
+- Access M3E tokens anywhere using the new ThemeData accessor:
+
+```dart
+final m3e = Theme.of(context).m3e; // ThemeData extension
+
+// Examples
+final br = m3e.shapes.round.sm;                 // BorderRadius
+final pad = EdgeInsets.all(m3e.spacing.md);      // Spacing scale
+final bg = m3e.colors.surfaceContainerHigh;      // Colors mapped to ColorScheme
+final curve = m3e.motion.emphasized;             // Motion/curves
+final title = m3e.typography.base.titleLarge;    // Typography
+```
+
+- Apply a rounded shape to a widget:
+
+```dart
+Widget roundedExample(BuildContext context) {
+  return Container(
+    decoration: BoxDecoration(
+      color: Theme.of(context).colorScheme.surface,
+      borderRadius: Theme.of(context).m3e.shapes.round.sm,
+    ),
+  );
+}
+```
+
+- Optional context sugar if you prefer:
+
+```dart
+// Provided by BuildContext extension in m3e_design
+final m3e = context.m3e;
+```
+
+Notes:
+- In debug, accessing `Theme.of(context).m3e` asserts if the extension isn't installed, helping catch setup issues.
+- In release, it safely falls back to sensible defaults derived from the active `ColorScheme`.
 
 ---
 
@@ -49,4 +128,4 @@ cd apps/gallery
 flutter run -d chrome
 ```
 
-_Last updated: 2025-10-23_
+_Last updated: 2025-10-25_