Add ruby 4 to test matrix and update local dev version

[andrcuns]

• Adds ruby 4.0 to test matrix and makes it default dev version
• Drop ruby 3.2 from test matrix as it has reached EOL

[andrcuns]

@baev I seem to have lost access to settings, could you remove 3.2 jobs from being required?

[Copilot]

Pull request overview

Updates the repository’s Ruby version policy by moving local development and CI testing forward to Ruby 4.0, while removing the EOL Ruby 3.2 from the test matrix.

Changes:

• Bump the default local Ruby version to 4.0.2 via .ruby-version.
• Update the GitHub Actions test matrix to add Ruby 4.0 and drop Ruby 3.2.
• Switch the Rubocop workflow job to run on Ruby 4.0.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.ruby-version	Updates the default local development Ruby to 4.0.2.
.github/workflows/test.yml	Updates CI to lint with Ruby 4.0 and test against Ruby 3.3/3.4/4.0.

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[Copilot]

This PR updates the test matrix to include Ruby 4.0 and makes it the default for linting, but .github/workflows/release.yml is still pinned to Ruby 3.4. If the intent is to move the repo default Ruby forward, the release workflow should likely be updated too to avoid building/releasing under an older Ruby than CI/dev.