Bug Fixes:
- Fixed holograms with ItemsAdder glyphs not being deletable
(SnakeYAML serialization errors were silently swallowed, leaving the hologram in holograms.yml even after /hologram remove)
- Fixed holograms reappearing after /oholograms reload due to a race
condition where the async unload ran AFTER the new load completed
- Fixed holograms with uppercase names not being removed from memory
during unload (map key mismatch stored as lowercase, removed as-is)
- Fixed pending hologram deletes being silently dropped on server stop
(file storage executor was shut down before the hologram thread finished)