Add initial configuration, tokens, and widgets for M3E components

- Introduced `.gitignore` and `.metadata` for apps and examples.
- Added Flutter/Dart analysis configurations (`analysis_options.yaml`).
- Implemented foundational tokens and themes for M3E (colors, shapes).
- Created base implementations for `IconButtonM3E` and `SplitButtonM3E`.
- Set up CI workflow (`ci.yaml`) to automate testing and analysis.

packages/button_m3e/lib/button_m3e.dart

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+library button_m3e;
+
+export 'src/enums.dart';
+export 'src/button_m3e.dart';
+export 'src/button_theme_m3e.dart';

packages/button_m3e/lib/src/button_m3e.dart

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+import 'package:flutter/material.dart';
+import 'enums.dart';
+import 'button_theme_m3e.dart';
+
+class ButtonM3E extends StatelessWidget {
+  const ButtonM3E({
+    super.key,
+    this.onPressed,
+    this.onLongPress,
+    this.leading,
+    this.trailing,
+    this.label,
+    this.labelText,
+    this.expand = false,
+    this.variant = ButtonM3EVariant.filled,
+    this.size = ButtonM3ESize.medium,
+    this.shapeFamily = ButtonM3EShapeFamily.round,
+    this.density = ButtonM3EDensity.regular,
+    this.semanticLabel,
+  }) : assert(label != null || labelText != null, 'Provide either label or labelText');
+
+  final VoidCallback? onPressed;
+  final VoidCallback? onLongPress;
+  final Widget? leading;
+  final Widget? trailing;
+  final Widget? label;
+  final String? labelText;
+  final bool expand;
+
+  final ButtonM3EVariant variant;
+  final ButtonM3ESize size;
+  final ButtonM3EShapeFamily shapeFamily;
+  final ButtonM3EDensity density;
+  final String? semanticLabel;
+
+  @override
+  Widget build(BuildContext context) {
+    final t = ButtonTokensAdapter(context);
+    final m = t.metrics(density);
+    final shape = t.shape(shapeFamily);
+
+    final (minH, pad) = switch (size) {
+      ButtonM3ESize.small => (m.heightSmall, m.paddingSmall),
+      ButtonM3ESize.medium => (m.heightMedium, m.paddingMedium),
+      ButtonM3ESize.large => (m.heightLarge, m.paddingLarge),
+    };
+
+    final style = _styleFor(context, t, shape, minH, pad);
+
+    final childLabel = label ?? Text(labelText!, overflow: TextOverflow.ellipsis);
+    final content = _buildContent(context, t, childLabel);
+
+    final Widget btn = switch (variant) {
+      ButtonM3EVariant.filled => FilledButton(style: style, onPressed: onPressed, onLongPress: onLongPress, child: content),
+      ButtonM3EVariant.tonal => FilledButton.tonal(style: style, onPressed: onPressed, onLongPress: onLongPress, child: content),
+      ButtonM3EVariant.outlined => OutlinedButton(style: style, onPressed: onPressed, onLongPress: onLongPress, child: content),
+      ButtonM3EVariant.text => TextButton(style: style, onPressed: onPressed, onLongPress: onLongPress, child: content),
+      ButtonM3EVariant.elevated => ElevatedButton(style: style, onPressed: onPressed, onLongPress: onLongPress, child: content),
+    };
+
+    if (!expand && semanticLabel == null) return btn;
+    final wrapped = expand ? SizedBox(width: double.infinity, child: btn) : btn;
+    if (semanticLabel == null) return wrapped;
+    return Semantics(
+      button: true,
+      label: semanticLabel,
+      child: wrapped,
+    );
+  }
+
+  ButtonStyle _styleFor(BuildContext context, ButtonTokensAdapter t, OutlinedBorder shape, double minH, EdgeInsetsGeometry pad) {
+    switch (variant) {
+      case ButtonM3EVariant.filled:
+        return FilledButton.styleFrom(
+          backgroundColor: t.bgFilled(),
+          foregroundColor: t.fgFilled(),
+          textStyle: t.labelStyle(),
+          minimumSize: Size(0, minH),
+          padding: pad,
+          shape: shape,
+        );
+      case ButtonM3EVariant.tonal:
+        return FilledButton.styleFrom(
+          backgroundColor: t.bgTonal(),
+          foregroundColor: t.fgTonal(),
+          textStyle: t.labelStyle(),
+          minimumSize: Size(0, minH),
+          padding: pad,
+          shape: shape,
+        );
+      case ButtonM3EVariant.outlined:
+        return OutlinedButton.styleFrom(
+          foregroundColor: t.fgOutlined(),
+          textStyle: t.labelStyle(),
+          minimumSize: Size(0, minH),
+          padding: pad,
+          shape: shape,
+          side: BorderSide(color: t.borderOutlined()),
+        );
+      case ButtonM3EVariant.text:
+        return TextButton.styleFrom(
+          foregroundColor: t.fgText(),
+          textStyle: t.labelStyle(),
+          minimumSize: Size(0, minH),
+          padding: pad,
+          shape: shape,
+        );
+      case ButtonM3EVariant.elevated:
+        return ElevatedButton.styleFrom(
+          backgroundColor: t.bgElevated(),
+          foregroundColor: t.fgElevated(),
+          textStyle: t.labelStyle(),
+          minimumSize: Size(0, minH),
+          padding: pad,
+          shape: shape,
+          elevation: _elevationFor(context, t),
+        );
+    }
+  }
+
+  double _elevationFor(BuildContext context, ButtonTokensAdapter t) {
+    // Simple mapping; can be themed further via tokens.
+    return 1.0;
+  }
+
+  Widget _buildContent(BuildContext context, ButtonTokensAdapter t, Widget childLabel) {
+    final style = t.labelStyle();
+    final text = DefaultTextStyle.merge(style: style, child: childLabel);
+    final hasLeading = leading != null;
+    final hasTrailing = trailing != null;
+
+    if (!hasLeading && !hasTrailing) return text;
+
+    return Row(
+      mainAxisSize: MainAxisSize.min,
+      mainAxisAlignment: MainAxisAlignment.center,
+      children: [
+        if (hasLeading) ...[leading!, const SizedBox(width: 8)],
+        Flexible(child: text),
+        if (hasTrailing) ...[const SizedBox(width: 8), trailing!],
+      ],
+    );
+  }
+}

packages/button_m3e/lib/src/button_m3e_widget.dart

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+import 'package:flutter/material.dart';
+import 'package:m3e_design/m3e_design.dart';
+
+class ButtonM3EWidget extends StatelessWidget {
+  const ButtonM3EWidget({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final m3e = context.m3e;
+    return Container(
+      padding: EdgeInsets.all(m3e.spacing.md),
+      decoration: BoxDecoration(
+        color: m3e.colors.surfaceStrong,
+        borderRadius: m3e.shapes.square.md,
+      ),
+      child: Text('Button placeholder', style: m3e.typography.base.labelLarge),
+    );
+  }
+}
+
+String _pascal(String s) => s
+    .split('_')
+    .map((p) => p.isEmpty ? '' : (p[0].toUpperCase() + p.substring(1)))
+    .join();

packages/button_m3e/lib/src/button_theme_m3e.dart

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+import 'package:flutter/material.dart';
+import 'package:m3e_design/m3e_design.dart';
+
+import 'enums.dart';
+
+@immutable
+class _ButtonMetrics {
+  final double heightSmall;
+  final double heightMedium;
+  final double heightLarge;
+  final EdgeInsetsGeometry paddingSmall;
+  final EdgeInsetsGeometry paddingMedium;
+  final EdgeInsetsGeometry paddingLarge;
+  final BorderSide outlinedBorder;
+  final double elevation;
+  const _ButtonMetrics({
+    required this.heightSmall,
+    required this.heightMedium,
+    required this.heightLarge,
+    required this.paddingSmall,
+    required this.paddingMedium,
+    required this.paddingLarge,
+    required this.outlinedBorder,
+    required this.elevation,
+  });
+}
+
+_ButtonMetrics _metricsFor(BuildContext context, ButtonM3EDensity density) {
+  final theme = Theme.of(context);
+  final m3e =
+      theme.extension<M3ETheme>() ?? M3ETheme.defaults(theme.colorScheme);
+  final sp = m3e.spacing;
+
+  // Heights based on Material 3 expectations; tweakable by density.
+  double hS = 36;
+  double hM = 40;
+  double hL = 48;
+
+  if (density == ButtonM3EDensity.compact) {
+    hS -= 4;
+    hM -= 4;
+    hL -= 4;
+  }
+
+  return _ButtonMetrics(
+    heightSmall: hS,
+    heightMedium: hM,
+    heightLarge: hL,
+    paddingSmall: EdgeInsets.symmetric(horizontal: sp.sm),
+    paddingMedium: EdgeInsets.symmetric(horizontal: sp.md),
+    paddingLarge: EdgeInsets.symmetric(horizontal: sp.lg),
+    outlinedBorder: BorderSide(color: m3e.colors.outline, width: 1.0),
+    elevation: 1.0,
+  );
+}
+
+class ButtonTokensAdapter {
+  ButtonTokensAdapter(this.context);
+  final BuildContext context;
+
+  M3ETheme get _m3e {
+    final t = Theme.of(context);
+    return t.extension<M3ETheme>() ?? M3ETheme.defaults(t.colorScheme);
+  }
+
+  // Colors
+  Color bgFilled() => _m3e.colors.primary;
+  Color fgFilled() => _m3e.colors.onPrimary;
+  Color bgTonal() => _m3e.colors.secondaryContainer;
+  Color fgTonal() => _m3e.colors.onSecondaryContainer;
+  Color bgElevated() => _m3e.colors.surfaceContainerLowest;
+  Color fgElevated() => _m3e.colors.primary;
+  Color fgText() => _m3e.colors.primary;
+  Color borderOutlined() => _m3e.colors.outline;
+  Color fgOutlined() => _m3e.colors.primary;
+  Color disabledFg() => _m3e.colors.onSurface.withValues(alpha: 0.38);
+  Color disabledBg() => _m3e.colors.onSurface.withValues(alpha: 0.12);
+
+  // Typography
+  TextStyle labelStyle() => _m3e.type.labelLarge;
+
+  // Shapes
+  OutlinedBorder shape(ButtonM3EShapeFamily family) {
+    if (family == ButtonM3EShapeFamily.round) {
+      return RoundedRectangleBorder(borderRadius: _m3e.shapes.round.lg);
+    }
+    // Square family should have sharp corners (no rounding)
+    return const RoundedRectangleBorder(borderRadius: BorderRadius.zero);
+  }
+
+  // Spacing & heights
+  _ButtonMetrics metrics(ButtonM3EDensity density) =>
+      _metricsFor(context, density);
+}

packages/button_m3e/lib/src/enums.dart

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+enum ButtonM3EVariant { filled, tonal, outlined, text, elevated }
+enum ButtonM3ESize { small, medium, large }
+enum ButtonM3EShapeFamily { round, square }
+enum ButtonM3EDensity { regular, compact }