Fix biome names and conditions

- Register readable client biome IDs while preserving saved registry identities.
- Audit the modded registry naming mixin.
- Return false from MythicMobs conditions while saved biome data loads.
- Cover biome naming and MythicMobs loading behavior with regression tests.

core/build.gradle

@@ -168,6 +168,8 @@ dependencies {
     testImplementation(libs.log4j.core)
     testRuntimeOnly(libs.paper.api)
     testImplementation(libs.multiverseCore)
+    testImplementation(libs.annotations)
+    testImplementation(libs.mythic)
 }
 
 tasks.named('test').configure {