fix(04-bugfix): enable IncludesAssetPack=true so plugin asset-pack is registered

Without this flag, JavaPlugin.setup0() skips AssetModule.registerPack(),
so bundled Items/*.json are never loaded into Item.getAssetMap(), causing
/gravityflip wand to fail with 'Item gravityflip_wand introuvable'.

src/main/resources/manifest.json

@@ -16,5 +16,5 @@
   "Dependencies": {},
   "OptionalDependencies": {},
   "DisabledByDefault": false,
-  "IncludesAssetPack": false
+  "IncludesAssetPack": true
 }