The r3-M1 fix was applied as a mechanical substring replacement and flipped
BOTH model_version conditions in the file; the independent room_wall_ids
invariant (#244/#252) silently stopped checking every v9+ document. Only the
opening_host requirement is scoped to model v8 — room_wall_ids is back to
'v8 and every later version', now pinned by its first regression test
(phantom wall_ids reported on v9 and v8; executed red on the broken
comparison, green after the fix).
Issue: #316
User-Visible: no