Improve generation and lifecycle safety

- Reduce terrain, noise, hydrology, and decorator sampling overhead.
- Reduce object transaction allocations while preserving rollback behavior.
- Optimize structure placement and cave anchor sampling.
- Parallelize Studio cache warmup and protect world entry and hotload recovery.
- Validate pack fingerprints and publish pack replacements atomically.
- Notify modded operators about outdated packs without synchronizing pack data.
- Harden world creation, loading, evacuation, and teleport failure recovery.
- Coalesce queued region flushes while preserving chunk save ordering.
- Remove obsolete mantle, pack, and cave planning code.
- Add regression tests and reusable gameplay fixtures.

core/build.gradle

@@ -379,8 +379,6 @@ List<String> unusedVolmLibClasses = [
     'art/arcane/volmlib/util/bukkit/Events',
     'art/arcane/volmlib/util/json/SingleCollectionTypeFactory',
     'art/arcane/volmlib/util/collection/StateList',
-    'art/arcane/iris/pack/IrisPack',
-    'art/arcane/iris/pack/IrisPackRepository',
     'art/arcane/iris/world/task/jobs/DownloadJob',
     'art/arcane/iris/world/task/jobs/JobCollection',
     'art/arcane/iris/world/task/jobs/ParallelQueueJob',