fix: use SRG client jar for securejarhandler minecraft module

ensureVersionJarForForge() was copying the vanilla Mojang jar
(obfuscated class names) to versions/<forgeId>/<forgeId>.jar.
securejarhandler creates the minecraft module from this jar, but
obfuscated names dont match SRG names like PreparableReloadListener.
The package is claimed by the module but class is not found → crash.

Now prioritizes the SRG-mapped client jar from Forge libraries
(client-*-srg.jar) which has Automatic-Module-Name: minecraft and
correct SRG class names. Falls back to vanilla jar only if SRG jar
is not found.

Also removed redundant -DlibraryDirectory already in manifest args.

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/launch/LaunchCommandBuilder.java

@@ -125,7 +125,6 @@ public class LaunchCommandBuilder {
                     }
                 }
 
-                command.add("-DlibraryDirectory=" + instance.getPath().resolve("libraries").toAbsolutePath());
                 command.add(getVanillaMainClass());
                 command.addAll(getVanillaGameArguments(options));
                 command.addAll(getModloaderLaunchArgs());
@@ -674,17 +673,15 @@ public class LaunchCommandBuilder {
      * Ensure the version jar exists at versions/<versionId>/<versionId>.jar
      * so that securejarhandler can create the "minecraft" module from it.
      *
-     * The Forge installer only creates the JSON at that path, not the jar.
+     * The version jar MUST contain SRG-mapped classes (not obfuscated Mojang
-     * We copy the vanilla version jar (e.g. versions/1.20.1/1.20.1.jar) there.
+     * names) and have Automatic-Module-Name: minecraft in its MANIFEST.MF.
+     * Without this, securejarhandler creates an automatic module from the
+     * filename, claims the net.minecraft.server.packs.resources package, but
+     * doesn't have SRG-named classes like PreparableReloadListener → crash.
      *
-     * securejarhandler reads Automatic-Module-Name: minecraft from the jar's
+     * Priority:
-     * MANIFEST.MF and creates a named "minecraft" module. This is the module
+     * 1. SRG-mapped client jar from Forge libraries (client-*-srg.jar)
-     * that Forge's code expects classes like PreparableReloadListener to be in.
+     * 2. Vanilla version jar (fallback, may cause module issues)
-     *
-     * Critical: the jar is NOT put on -cp. Only the copy at versions/<versionId>/
-     * is used by securejarhandler. The original 1.20.1.jar must stay off the
-     * classpath to prevent automatic module _1._20._1 from being created,
-     * which would conflict with the "minecraft" module (split-package error).
      */
     private void ensureVersionJarForForge() throws IOException {
         String versionId = getVersionId();
@@ -699,16 +696,53 @@ public class LaunchCommandBuilder {
             return;
         }
 
-        // Source: the vanilla version jar
+        Files.createDirectories(targetDir);
-        Path sourceJar = versionsDir.resolve(mcVersion).resolve(mcVersion + ".jar");
+
-        if (!Files.exists(sourceJar) || !isValidJar(sourceJar)) {
+        // Priority 1: SRG-mapped client jar from Forge libraries
-            System.out.println(ZAnsi.yellow("  Vanilla version jar not found at " + sourceJar));
+        // This jar has Automatic-Module-Name: minecraft and correct SRG class names
+        Path srgJar = findSrgClientJar();
+        if (srgJar != null && isValidJar(srgJar)) {
+            Files.copy(srgJar, targetJar);
+            System.out.println(ZAnsi.green("  Copied SRG client jar for securejarhandler: " + srgJar.getFileName() + " → " + targetJar));
+            return;
+        }
+
+        // Fallback: vanilla version jar (obfuscated names, may cause module issues)
+        Path sourceJar = versionsDir.resolve(mcVersion).resolve(mcVersion + ".jar");
+        if (!Files.exists(sourceJar) || !isValidJar(sourceJar)) {
+            System.out.println(ZAnsi.yellow("  No suitable version jar found (SRG or vanilla)"));
             return;
         }
 
-        Files.createDirectories(targetDir);
         Files.copy(sourceJar, targetJar);
-        System.out.println(ZAnsi.green("  Copied version jar for securejarhandler: " + sourceJar.getFileName() + " → " + targetJar));
+        System.out.println(ZAnsi.yellow("  Copied vanilla jar (fallback) for securejarhandler: " + sourceJar.getFileName() + " → " + targetJar));
+    }
+
+    /**
+     * Find the SRG-mapped client jar in Forge libraries.
+     * Path: libraries/net/minecraftforge/client/<mcVersion>-<mcpVersion>/client-<mcVersion>-<mcpVersion>-srg.jar
+     * This jar contains SRG-mapped classes and has Automatic-Module-Name: minecraft.
+     */
+    private Path findSrgClientJar() {
+        Path librariesDir = instance.getPath().resolve("libraries");
+        Path mcDir = librariesDir.resolve("net/minecraftforge/client");
+        if (!Files.exists(mcDir)) return null;
+
+        String mcVersion = instance.getMinecraftVersion();
+        try (var stream = Files.list(mcDir)) {
+            return stream
+                .filter(Files::isDirectory)
+                .filter(dir -> dir.getFileName().toString().startsWith(mcVersion + "-"))
+                .flatMap(dir -> {
+                    try { return Files.list(dir); } catch (Exception e) { return java.util.stream.Stream.empty(); }
+                })
+                .filter(p -> p.getFileName().toString().endsWith("-srg.jar"))
+                .filter(this::isValidJar)
+                .findFirst()
+                .orElse(null);
+        } catch (Exception e) {
+            return null;
+        }
     }
 
     /**