feat(dist): shaded jar aggregator

Bundles core + ecs + binding into a single shaded JAR via
com.gradleup.shadow. Regular jar stays enabled so composite builds
in examples/ can consume project(":dist") directly.

dist/build.gradle.kts

@@ -0,0 +1,26 @@
+plugins {
+    `java-library`
+    alias(libs.plugins.shadow)
+}
+
+dependencies {
+    api(project(":core"))
+    api(project(":ecs"))
+    api(project(":binding"))
+}
+
+java {
+    toolchain { languageVersion.set(JavaLanguageVersion.of(25)) }
+}
+
+tasks.withType<JavaCompile>().configureEach { options.release.set(24) }
+
+tasks {
+    shadowJar {
+        archiveBaseName.set("async")
+        archiveClassifier.set("")
+        mergeServiceFiles()
+    }
+    // Regular jar stays enabled so composite builds (examples/) can consume project(":dist") directly.
+    build { dependsOn(shadowJar) }
+}