dart-flutter-sdk-upgrade

# VGV Flutter/Dart SDK Upgrade — Quick Reference One PR per project. Only CI workflow and `pubspec.yaml` changes — no logic, no dependency version bumps, no test changes. --- ## Core Standards Apply these standards to ALL SDK upgrade work: - **Flutter and Dart versions differ** — a Flutter release ships a Dart SDK whose version number is unrelated to it, and the pubspec `sdk:` constraint takes the Dart number, never the Flutter one. Look the pairing up in the release archive at <https://docs.flutter.dev/install/archive> - **Never state a bundled Dart version from memory** — not from recall, not by inference from the Flutter number, and not from an example in this file. Either the user supplied the Dart version, or you read it off the archive, or you ask. There is no fourth source - **Flutter CI uses `MAJOR.MINOR.x`** — no caret, `.x` wildcard resolves to latest patch - **Dart CI uses exact patch** — `MAJOR.MINOR.PATCH`, no caret, no wildcard - **pubspec pins exact patch** — use `^MAJOR.MINOR.PATCH` with the specific patch version - **Pure Dart packages** — use the Dart version directly, no Flutter mapping needed. The CI key is `dart_sdk` in `dart_package.yml`, not `flutter_version` in `flutter_package.yml`, and the environment block gets `sdk:` with no `flutter:` line beside it - **Write the CI block even without the file** — the reusable workflow and its version key are determined by the package type, so a workflow you have not seen is still a known shape. Produce the `...