## Overview
This PR prepares the release of version 1.3.0 for all packages, updating
CHANGELOGs and package versions to reflect the changes made since
v1.2.0.

## Changes
- Updated CHANGELOG.md for all packages (playbook, playbook_generator,
playbook_snapshot, playbook_ui) to include v1.3.0 release notes
- Bumped package versions from 1.2.0 to 1.3.0 in all pubspec.yaml files
- Updated README.md requirements section to reflect minimum Dart 3.9.0+
and Flutter 3.35.0+

### Release Notes Summary
- **SDK Updates**: Dart constraint updated to `^3.9.0`, Flutter
constraint to `>=3.35.0`
- **Analysis**: Migrated to `very_good_analysis` 10.0.0
- **Infrastructure**: Migrated from Melos workspace to Dart workspace
configuration
- **CI/CD**: Migrated from `subosito/flutter-action` to
`jdx/mise-action`
- **Version Management**: Added `.mise.toml` for Flutter 3.35.5
- **Code Quality**: Refactored code to use pattern matching instead of
runtimeType switch (playbook_snapshot, playbook_ui)

## Test Instructions
1. Verify CHANGELOG.md files contain accurate v1.3.0 release notes for
all packages
2. Confirm all pubspec.yaml files show version 1.3.0
3. Verify README.md shows correct minimum requirements (Dart 3.9.0+,
Flutter 3.35.0+)
4. Run `dart pub get` to ensure workspace resolution works correctly
5. Run `melos analyze` to verify no analysis issues
6. Run `melos test` to ensure all tests pass

## References
- Related to recent workspace configuration updates (#153)
- Follows semantic versioning for minor release