- Rename "type" -> "$type" (first key, required for STJ polymorphism) in
all 109 spawn JSON files (5,612 records).
- Convert "homeRange" + "location" -> "spawnBounds" object, dropping homeRange.
Runtime keeps reading homeRange so un-migrated/external files still load.
- Add BoundsEquivalenceTests (hr=0/1/3/7) validating that the script's toBounds
formula produces the same Rectangle3D as the runtime homeRange path.
- Add MigratedDataLoadTests loading a real migrated file as List<SpawnerDto>
and round-tripping each DTO through ToSpawner().
- Add tools/spawner-json-migrate/migrate.mjs (offline Node script).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
### Summary
- Add z-restricted spawnBounds to 35 spawners across 15 files to prevent creatures from spawning on incorrect floors
- Building spawners (Pyramid, Fire dungeon, Shame, Vendors) use minZ = spawner_z to prevent spawning below
- Ground level spawners (Graveyards, Outdoors, Tokuno) use minZ = -128 for natural terrain variation
- Multi-floor structures in Ilshenar use floor-specific Z restrictions
### Test plan
- Verify spawners in Fire dungeon building don't spawn creatures on floors below
- Verify Pyramid spawners keep creatures on their respective levels
- Verify ground level spawners (graveyards, outdoors) still spawn correctly on terrain
- Check Ilshenar multi-floor structure spawns creatures on correct floors
