feat(stealth): migrate distribution to Java 25 and Purpur

BREAKING CHANGE: New releases require Java 25/Purpur 26.2 and use purpur-stealth-<version>.jar. Runtime SpigotStealth identity, existing data and permissions remain unchanged. Replace the old JAR rather than installing both.

src/test/java/games/dmg/spigotstealth/DeliveryConfigurationTest.java

@@ -13,7 +13,7 @@ class DeliveryConfigurationTest {
         String workflow = Files.readString(Path.of(".gitea/workflows/ci.yml"));
         assertTrue(workflow.contains("./gradlew clean check jar"));
         assertTrue(workflow.contains("commitlint"));
-        assertTrue(workflow.contains("spigot-stealth-${{ github.sha }}"));
+        assertTrue(workflow.contains("purpur-stealth-${{ github.sha }}"));
     }
 
     @Test
@@ -21,7 +21,7 @@ class DeliveryConfigurationTest {
         String workflow = Files.readString(Path.of(".gitea/workflows/release.yml"));
         assertTrue(workflow.contains("semantic-release"));
         assertTrue(workflow.contains("-PreleaseVersion=\"$VERSION\""));
-        assertTrue(workflow.contains("spigot-stealth-${VERSION}.jar"));
+        assertTrue(workflow.contains("purpur-stealth-${VERSION}.jar"));
         assertTrue(workflow.contains("/releases/${release_id}/assets"));
     }
 }

src/test/java/games/dmg/spigotstealth/PurpurDistributionTest.java

@@ -0,0 +1,53 @@
+package games.dmg.spigotstealth;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.io.DataInputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.jar.JarFile;
+import org.junit.jupiter.api.Test;
+import org.yaml.snakeyaml.Yaml;
+
+class PurpurDistributionTest {
+    @Test
+    void packagesNewNameWithoutChangingRuntimeIdentityOrBundlingTheApi() throws Exception {
+        Path artifact = Path.of(System.getProperty("distribution.jar"));
+        String version = System.getProperty("distribution.version");
+        assertEquals("purpur-stealth-" + version + ".jar", artifact.getFileName().toString());
+        try (var jar = new JarFile(artifact.toFile())) {
+            Map<?, ?> metadata = new Yaml().load(jar.getInputStream(jar.getJarEntry("plugin.yml")));
+            assertEquals(version, metadata.get("version"));
+            assertEquals("SpigotStealth", metadata.get("name"), "Retain the data directory and persistent namespace");
+            assertEquals("games.dmg.spigotstealth.SpigotStealthPlugin", metadata.get("main"));
+            assertTrue(((Map<?, ?>) metadata.get("permissions")).containsKey("spigotstealth.admin"));
+            assertFalse(jar.stream().anyMatch(entry -> entry.getName().startsWith("org/bukkit/")
+                || entry.getName().startsWith("org/purpurmc/") || entry.getName().endsWith("Test.class")));
+        }
+    }
+
+    @Test
+    void pluginBytecodeTargetsJava25() throws Exception {
+        try (var jar = new JarFile(System.getProperty("distribution.jar"));
+             var bytecode = new DataInputStream(jar.getInputStream(
+                 jar.getJarEntry("games/dmg/spigotstealth/SpigotStealthPlugin.class")))) {
+            assertEquals(0xCAFEBABE, bytecode.readInt());
+            bytecode.readUnsignedShort();
+            assertEquals(69, bytecode.readUnsignedShort());
+        }
+    }
+
+    @Test
+    void releaseAndCiAgreeWithThePurpurDistributionNameAndToolchain() throws Exception {
+        String build = Files.readString(Path.of("build.gradle.kts"));
+        assertTrue(build.contains("purpur-api:26.2.build.2618-stable"));
+        assertFalse(build.contains("org.spigotmc:spigot-api"));
+        for (String workflow : new String[] {"ci.yml", "release.yml"}) {
+            String content = Files.readString(Path.of(".gitea/workflows", workflow));
+            assertTrue(content.contains("java-version: 25"));
+            assertTrue(content.contains("purpur-stealth-"), workflow);
+            assertFalse(content.contains("spigot-stealth-"), workflow);
+        }
+    }
+}