_teardown_session swallows agent.close() failures, so a "row stays open"
assertion alone is green even when close() aborted before
_finalize_owned_session_row. Assert the one side effect only that finalizer
produces (_owns_session_db cleared), give the stub the _memory_manager attr
close() reads directly, and assert the flag is untouched on the control
paths. Rename the sole-owner cross-process test to what it now asserts.
kshitijk4poor
f0b2ba4160