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- Notify modded operators about outdated packs without synchronizing pack data.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.

adapters/bukkit/plugin/src/test/gameplay/noise-pack/biomes/flat.json

@@ -0,0 +1,32 @@
+{
+  "name": "Flat",
+  "derivative": "minecraft:plains",
+  "vanillaDerivative": "minecraft:plains",
+  "layers": [
+    {
+      "minHeight": 1,
+      "maxHeight": 1,
+      "palette": [
+        {
+          "block": "minecraft:lime_wool"
+        }
+      ]
+    },
+    {
+      "minHeight": 384,
+      "maxHeight": 384,
+      "palette": [
+        {
+          "block": "minecraft:green_concrete"
+        }
+      ]
+    }
+  ],
+  "generators": [
+    {
+      "generator": "flat",
+      "min": 64,
+      "max": 96
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/noise-pack/dimensions/noise-fixture.json

@@ -0,0 +1,28 @@
+{
+  "name": "Noise Sources",
+  "version": 1,
+  "mode": {
+    "type": "OVERWORLD"
+  },
+  "regions": [
+    "flat"
+  ],
+  "focusRegion": "flat",
+  "focus": "flat",
+  "landChance": 1,
+  "environment": "NORMAL",
+  "dimensionHeight": {
+    "min": -64,
+    "max": 320
+  },
+  "logicalHeight": 384,
+  "fluidHeight": 0,
+  "bedrock": false,
+  "rockPalette": {
+    "palette": [
+      {
+        "block": "minecraft:red_concrete"
+      }
+    ]
+  }
+}

adapters/bukkit/plugin/src/test/gameplay/noise-pack/expressions/terrain.json

@@ -0,0 +1,3 @@
+{
+  "expression": "0.5 + sin(x * 0.15) * 0.25 + cos(y * 0.13) * 0.25"
+}

adapters/bukkit/plugin/src/test/gameplay/noise-pack/generators/flat.json

@@ -0,0 +1,22 @@
+{
+  "interpolator": {
+    "function": "NONE",
+    "horizontalScale": 1
+  },
+  "seed": 310,
+  "composite": [
+    {
+      "seed": 310,
+      "style": {
+        "expression": "terrain"
+      }
+    },
+    {
+      "seed": 311,
+      "style": {
+        "style": "CLOVER_HERMITE",
+        "zoom": 0.1
+      }
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/noise-pack/regions/flat.json

@@ -0,0 +1,12 @@
+{
+  "name": "Flat",
+  "landBiomes": [
+    "flat"
+  ],
+  "seaBiomes": [
+    "flat"
+  ],
+  "shoreBiomes": [
+    "flat"
+  ]
+}