controller: investigate owner references and garbage collection

Kubernetes provides built-in mechanisms for ownership referencing and garbage collection. Should we be using this for tests and/or resources when their controller is deleted? Should tests 'own' resources?

No files, tests, or entry points are identified in the issue. Start by reviewing how the controller handles tests and resources, then compare that behavior with Kubernetes ownership references and garbage collection. Done means reaching a clear decision about controller-deletion cleanup and whether tests should own resources, with scope agreed for any follow-up work.

Written by the indexing model from the issue text.