Gate r1 quality finding: test_empty_ghost_session_does_not_block_title
read as "ghosts never block", but three of its four rows assert the
opposite. Rename it to
test_title_conflict_yields_only_to_ended_empty_visible_holder, make the
holder_messages count a holder_has_message bool (only zero vs non-zero
matters), and state the rule in the docstring: a holder yields only when
ended, empty, visible and unarchived; every other holder conflicts.
2eceb02755