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/icon_button_m3e/README.md

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+# icon_button_m3e
+
+Expressive Material 3 icon button for Flutter — `IconButtonM3E` — with
+five sizes (XS–XL), four variants (standard, filled, tonal, outlined),
+round/square shapes, toggle support, and guaranteed 48×48dp tap targets
+(even when visual size is 32/40).
+
+## Highlights
+
+- Sizes: `M3EIconButtonSize` = XS, SM, MD, LG, XL
+- Widths: `M3EIconButtonWidth` = default, narrow, wide
+- Variants: standard, filled, tonal, outlined
+- Shapes: round (pill) or square (rounded rect)
+- Toggle: `isSelected` + `selectedIcon`
+- A11y: min 48×48dp hit target; semantics label/selected state
+- Tokens: centralized static values in `M3EIconButtonTokens` (no ThemeExtension)
+
+## Install
+
+```yaml
+dependencies:
+  icon_button_m3e:
+    path: ../icon_button_m3e  # or from pub once published
+```
+
+## Quick Start
+
+```dart
+import 'package:icon_button_m3e/icon_button_m3e.dart';
+
+IconButtonM3E(
+  variant: IconButtonM3EVariant.filled,
+  size: M3EIconButtonSize.md,
+  width: M3EIconButtonWidth.defaultWidth,
+  icon: const Icon(Icons.mic),
+  tooltip: 'Start recording',
+  onPressed: () {},
+);
+```
+
+### Toggle
+
+```dart
+bool isFav = false;
+
+IconButtonM3E(
+  variant: IconButtonM3EVariant.tonal,
+  isSelected: isFav,
+  icon: const Icon(Icons.favorite_border),
+  selectedIcon: const Icon(Icons.favorite),
+  tooltip: isFav ? 'Remove from favorites' : 'Add to favorites',
+  onPressed: () => setState(() => isFav = !isFav),
+);
+```
+
+## Sizing
+
+- Visual container sizes come from tokens: `M3EIconButtonTokens.visual[size][width]`.
+- Minimum interactive target sizes come from `M3EIconButtonTokens.target[size][width]`.
+  - XS/SM enforce at least 48×48; others match their visual sizes.
+- Icon glyph sizes are in `M3EIconButtonTokens.icon[size]`.
+
+For example (default width):
+- XS: 32×32 visual, 48×48 target
+- SM: 40×40 visual, 48×48 target (SM wide: 52×48)
+- MD: 56×56
+- LG: 96×96
+- XL: 136×136
+
+## Colors and shapes
+
+- Colors are derived from your `ThemeData.colorScheme`:
+  - standard: transparent bg, onSurfaceVariant fg (selected uses primary)
+  - filled: primary bg, onPrimary fg
+  - tonal: secondaryContainer bg, onSecondaryContainer fg
+  - outlined: transparent bg, primary fg, outline border
+- Shapes: `M3EIconButtonShapeVariant.round` (pill) or `.square` (rounded square).
+  - Pressed state uses a shared, more-square radius per size.
+  - If used as a toggle, selected state flips round/square for expressive feel.
+
+## Example
+
+Run the example app:
+
+```sh
+cd example
+flutter run
+```
+
+## License
+
+MIT