👷 add Minimum Dart CI workflow

[techouse]

This pull request introduces a new GitHub Actions workflow for testing packages against their minimum supported Dart SDK versions, and also updates permissions in existing workflow files for improved security.

CI/CD Improvements:

• Added a new workflow file .github/workflows/minimum_dart.yml to automatically test each package (chopper, chopper_built_value, chopper_generator) against its minimum Dart SDK version, across both VM and Chrome platforms. This ensures ongoing compatibility with the lowest supported Dart versions.

Security Enhancements:

• Updated the permissions in .github/workflows/publish.yml and .github/workflows/publish_dry_run.yml from read-all to a more restrictive contents: read, following GitHub's best practices for least privilege. [1] [2]

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.05%. Comparing base (8f1c7f9) to head (2d3f9d7).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #709   +/-   ##
========================================
  Coverage    99.05%   99.05%           
========================================
  Files           23       23           
  Lines          530      530           
========================================
  Hits           525      525           
  Misses           5        5           

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[Copilot]

Pull request overview

Adds a new GitHub Actions workflow to continuously validate that each package in the repo still works on its minimum supported Dart SDK version, and tightens default workflow token permissions for publish workflows.

Changes:

• Added Minimum Dart CI workflow to run analyze/tests against each package’s minimum Dart SDK (VM and Chrome where configured).
• Reduced default GITHUB_TOKEN permissions in publish workflows from read-all to contents: read.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/minimum_dart.yml	New CI workflow to derive each package’s minimum Dart SDK from pubspec.yaml and run tests/analyze accordingly.
.github/workflows/publish.yml	Restricts default workflow token permissions to least-privilege (contents: read).
.github/workflows/publish_dry_run.yml	Restricts default workflow token permissions to least-privilege (contents: read).

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[techouse]

Codecov tripping because of -0.06% 🤣

@JEuler sadly I can't tighten the permissions in .github/workflows/dart.yml because it's generated by mono_repo and hand-editing it makes

mono_repo generate --validate

fail.