Added treasure loot coverage

- Gameplay opens normal and copper chests before inspecting loot
- Map markers and saved centers match verified structure targets
- Missing and disabled destinations retain unrelated chest loot
- Storage variants, insertion rollback, region ownership, and resource reloads have runtime assertions
- Separate data packs cover Minecraft 26.2 and 26.3 loot formats

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/pack.mcmeta

@@ -0,0 +1,13 @@
+{
+  "pack": {
+    "description": "Treasure map gameplay fixtures",
+    "min_format": [
+      121,
+      0
+    ],
+    "max_format": [
+      121,
+      0
+    ]
+  }
+}