When no Geb tests exist, do not start a container

There may be an issue where if no Geb tests are defined, we still start a container / browser. We need to enhance our spock extension so it doesn't require a container if no tests are present.

Start by locating the Spock extension responsible for starting the container or browser, then inspect how it discovers Geb tests. Verify the behavior when no Geb tests are defined and use the existing test suite to confirm that no container starts in that case.

Written by the indexing model from the issue text.