Add support for github refs when downloading Ark

[lionel-]

Written with the help of Claude as agent.

Adds support for specifying Ark versions as github refs in package.json:

  "positron": {
    "binaryDependencies": {
      "ark": "posit-dev/ark@main"                  // Use the main branch
      "ark": "posit-dev/ark@experimental-feature"  // Use a feature branch
      "ark": "posit-dev/ark@a1b2c3d"               // Use a specific commit
      "ark": "posit-dev/ark@v0.1.183"              // Use a specific tag
    }
  }

The github revision is downloaded, built, and installed.

This allows CI-testing a branch in the Positron repo against a branch in the Ark repo without having to release Ark first. Releasing just for the purpose of testing is really not ideal as the feature might not be working well yet and other developers might need to do further Ark releases to make progress with their own work.

To prevent committing a dev ref that might have been forgotten in the package.json file, a github action watches changes to this file and checks that a release version is used.

Release Notes

New Features

• N/A

Bug Fixes

• N/A

QA Notes

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical

^{readme  valid tags}