Add clj-kondo linter workflow

[danielhvs]

Purpose

Adds a GitHub Actions workflow running clj-kondo on PRs to main, mirroring the setup in pyrecast-gcp-deployment.

1. Triggers on changes to src/**/*.clj, test/**/*.clj, deps.edn, or the workflow itself.
2. Installs clj-kondo via DeLaGuardo/setup-clojure@13.6.0.
3. Runs clj-kondo --lint src test --fail-level error.
4. Concurrency group cancels superseded runs on the same ref.

This enforces the existing PR checklist item "Code passes linter rules".

Related Issues

None.

Submission Checklist

• Included Jira issue in the PR title
• Code passes linter rules (clj-kondo --lint src)
• No new reflection warnings (no Clojure code changed)

Testing

1. Given a clean clone of main, When running clj-kondo --lint src test --fail-level error, Then 9 files lint with 0 errors and 0 warnings and exit code 0.
2. Given a PR touching a .clj file under src or test, When the PR opens against main, Then the clj-lint job runs and fails only on error-level findings.