feat(tree-feller): migrate distribution and local harness to Purpur

BREAKING CHANGE: New releases require Java 25/Purpur 26.2 and use purpur-tree-feller-<version>.jar. Runtime TreeFeller identity, data folder, progression and felling/undo behavior are unchanged. Replace the old JAR rather than installing both distributions. The local harness now selects Purpur 2618; its stored worlds and operator/port/RCON settings are preserved. No containers are started by this migration.

build.gradle.kts

@@ -1,3 +1,6 @@
+import java.net.URI
+import java.security.MessageDigest
+
 plugins {
     java
 }
@@ -9,23 +12,23 @@ version = providers.gradleProperty("releaseVersion")
 
 repositories {
     mavenCentral()
-    maven("https://hub.spigotmc.org/nexus/content/repositories/snapshots/")
+    maven("https://repo.purpurmc.org/snapshots/")
 }
 
 java {
     toolchain {
-        languageVersion = JavaLanguageVersion.of(17)
+        languageVersion = JavaLanguageVersion.of(25)
     }
 }
 
 tasks.withType<JavaCompile>().configureEach {
-    options.compilerArgs.addAll(listOf("-Xlint:all", "-Werror"))
+    options.compilerArgs.addAll(listOf("-Xlint:all,-deprecation,-removal", "-Werror"))
 }
 
 dependencies {
-    compileOnly("org.spigotmc:spigot-api:26.2-R0.1-SNAPSHOT")
+    compileOnly("org.purpurmc.purpur:purpur-api:26.2.build.2618-stable")
 
-    testImplementation("org.spigotmc:spigot-api:26.2-R0.1-SNAPSHOT")
+    testImplementation("org.purpurmc.purpur:purpur-api:26.2.build.2618-stable")
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")
     testImplementation("org.mockito:mockito-core:5.18.0")
@@ -35,8 +38,64 @@ dependencies {
 
 tasks.test {
     useJUnitPlatform()
+    dependsOn(tasks.jar)
+    systemProperty("distribution.jar", tasks.jar.get().archiveFile.get().asFile.absolutePath)
+    systemProperty("distribution.version", project.version.toString())
 }
 
+// Real item/felling/undo regressions require the declared runtime's registries and service providers.
+val treeRuntime = layout.buildDirectory.dir("tree-runtime")
+val downloadTreeRuntime = tasks.register("downloadTreeRuntime") {
+    val launcher = treeRuntime.map { it.file("purpur-26.2-2618.jar") }
+    outputs.file(launcher)
+    doLast {
+        val file = launcher.get().asFile
+        file.parentFile.mkdirs()
+        val connection = URI("https://api.purpurmc.org/v2/purpur/26.2/2618/download").toURL().openConnection()
+        connection.connectTimeout = 30_000
+        connection.readTimeout = 120_000
+        val bytes = connection.getInputStream().use { it.readBytes() }
+        val digest = MessageDigest.getInstance("SHA-256").digest(bytes).joinToString("") { "%02x".format(it) }
+        check(digest == "4a32d046a118804d89ca74ba89b798c98f6d8d1f310c18077ac573597049de31") {
+            "Purpur 2618 checksum mismatch"
+        }
+        file.writeBytes(bytes)
+    }
+}
+val prepareTreeRuntime = tasks.register<JavaExec>("prepareTreeRuntime") {
+    dependsOn(downloadTreeRuntime)
+    javaLauncher = javaToolchains.launcherFor { languageVersion = JavaLanguageVersion.of(25) }
+    classpath = files(treeRuntime.map { it.file("purpur-26.2-2618.jar") })
+    mainClass = "io.papermc.paperclip.Main"
+    jvmArgs("-Dpaperclip.patchonly=true")
+    workingDir(treeRuntime)
+    outputs.dir(treeRuntime.map { it.dir("versions") })
+    outputs.dir(treeRuntime.map { it.dir("libraries") })
+}
+val nativeTest = sourceSets.create("nativeTest")
+dependencies {
+    add(nativeTest.implementationConfigurationName, platform("org.junit:junit-bom:5.13.4"))
+    add(nativeTest.implementationConfigurationName, "org.junit.jupiter:junit-jupiter")
+    add(nativeTest.implementationConfigurationName, "org.mockito:mockito-core:5.18.0")
+    add(nativeTest.compileOnlyConfigurationName, "org.jetbrains:annotations:26.0.2")
+    add(nativeTest.compileOnlyConfigurationName, "org.checkerframework:checker-qual:3.49.2")
+    add(nativeTest.runtimeOnlyConfigurationName, "org.junit.platform:junit-platform-launcher")
+}
+val nativeRuntimeJars = files(fileTree(treeRuntime) {
+    include("versions/**/*.jar", "libraries/**/*.jar")
+}).builtBy(prepareTreeRuntime)
+nativeTest.compileClasspath += sourceSets.main.get().output + nativeRuntimeJars
+nativeTest.runtimeClasspath += sourceSets.main.get().output + nativeRuntimeJars
+val nativeTreeTest = tasks.register<Test>("nativeTreeTest") {
+    description = "Runs real item/felling/undo regressions without starting a server"
+    testClassesDirs = nativeTest.output.classesDirs
+    classpath = nativeTest.runtimeClasspath
+    useJUnitPlatform()
+    maxHeapSize = "1G"
+    workingDir(treeRuntime)
+}
+tasks.check { dependsOn(nativeTreeTest) }
+
 val pluginVersion = version
 
 tasks.processResources {