Pushes to feature branches built twice (push and pull request) and Check Codes
repeated the compile in a second workflow. Build now runs only on main, tags and
pull requests, cancels older runs of the same ref, folds checkstyle and
checkTranslations into the single Gradle invocation, caches the wrapper download
and skips apt when xvfb is installed.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>