delete_marker_definition removed the def but left the inherited global-*
copies on every link: it called stop_marker(), which rejects inherited
markers (409), and the ControllerError was swallowed as a warning. The
orphaned copies were in-memory only (_persist_markers filters inherited
markers) so a restart hid the symptom, but during a running session they
were undeletable via either the per-link or project API.
Add the same inherited=True bypass that update_marker already has, and
pass it from the def-delete fan-out so the copies are removed for real.