- Add ImportLocation/ImportMap read-only accessors to BaseSpawner.Json.cs
exposing _jsonLocation/_jsonMap for the importer post-STJ-deserialization.
- Rewrite ImportJsonSpawners to deserialize List<BaseSpawner> directly via
SpawnerJsonSerializer.Options (polymorphic on $type), eliminating
DynamicJson + AssemblyHandler.FindTypeByName + CreateInstance<ISpawner>.
- Enforce cleanup contract: every deserialized spawner (registered in World
at Map.Internal by STJ) is either MoveToWorld'd or Delete()'d — map==null/
Internal guard Deletes, inner catch Deletes on placement failure.
- Add internal ImportFile seam for testability (from=null safe; only used in
JsonException path which valid files never hit).
- Add ImportCleanupTests: valid placement, no-map orphan rejected, duplicate
location replaced — all with rigorous finally cleanup.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>