fix: improve threaded world compatibility and chunk reads in 1.1.15

Add regression tests and per-dimension progress diagnostics. Document the unresolved C2ME random-initialization redirect conflict.

build.gradle

@@ -76,6 +76,12 @@ dependencies {
     implementation "net.neoforged:neoforge:${neo_version}"
 }
 
+// Opt-in isolated runtime fixture; excluded from normal builds.
+if (providers.gradleProperty('interactionRegression').isPresent()) {
+    sourceSets.main.java.srcDir('tests/integration')
+    sourceSets.main.java.exclude('**/ChunkHandoffRegression.java')
+}
+
 tasks.withType(ProcessResources).configureEach {
     var replaceProperties = [
             minecraft_version   : minecraft_version,
@@ -107,3 +113,26 @@ idea {
         downloadJavadoc = true
     }
 }
+
+// Pure-Java scheduling regressions run in check without bootstrapping Minecraft.
+def regressionClasses = layout.buildDirectory.dir('regression')
+tasks.register('compileConcurrencyRegression', JavaCompile) {
+    source = files('tests/TaskBarrierRegression.java', 'tests/ManagedFutureAwaitRegression.java',
+            'src/main/java/dev/modzuozhi/core/compat/TaskBarrier.java',
+            'src/main/java/dev/modzuozhi/core/compat/ManagedFutureAwait.java',
+            'src/main/java/dev/modzuozhi/core/compat/PauseOwnership.java', 'tests/PauseOwnershipRegression.java',
+            'src/main/java/dev/modzuozhi/core/compat/TickProgress.java', 'tests/TickProgressRegression.java')
+    classpath = files()
+    destinationDirectory = regressionClasses
+}
+['TaskBarrierRegression', 'ManagedFutureAwaitRegression', 'PauseOwnershipRegression', 'TickProgressRegression'].each { regressionMain ->
+    def regressionTask = tasks.register("run${regressionMain}", JavaExec) {
+        dependsOn 'compileConcurrencyRegression'
+        classpath = files(regressionClasses)
+        mainClass = regressionMain
+        javaLauncher = javaToolchains.launcherFor {
+            languageVersion = JavaLanguageVersion.of(21)
+        }
+    }
+    tasks.named('check') { dependsOn regressionTask }
+}