Regression test that deserializes every spawned JSON file under
Data/Spawns/ via SpawnerDto, calls ToSpawner() to build the live
spawner, and deletes it to prevent world leaks. Catches both JSON
deserialization failures and exceptions during spawner construction,
collecting failures per file. Any failure names the offending file
and is a real migration defect, not a test weakness.
All 484 tests pass including the new AllSpawnFilesLoadTests.
dc655bbb19