fix: ensure version jar exists for Forge to prevent _1._20._1 module name

findVersionJar() falls back to versions/1.20.1/1.20.1.jar when the Forge
version jar doesnt exist. Filename 1.20.1.jar produces automatic module _1._20._1
which conflicts with module minecraft (split-package on net.minecraft.server).

Fix: ensureVersionJarForForge() copies vanilla jar to versions/<versionId>/
<versionId>.jar before findVersionJar() is called. Vanilla jar has
Automatic-Module-Name: minecraft so it becomes module minecraft, not _1._20._1.

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

@@ -59,6 +59,11 @@ public class LaunchCommandBuilder {
             // defines all of these. This matches AstralRinth's approach.
             System.out.println(ZAnsi.cyan("  Forge/NeoForge: using version.json args with placeholder substitution"));
 
+            // Ensure version jar exists at versions/<versionId>/<versionId>.jar
+            // so securejarhandler creates module "minecraft" (from Automatic-Module-Name)
+            // instead of "_1._20._1" (automatic module from filename 1.20.1.jar).
+            ensureVersionJarForForge();
+
             // Build classpath from manifest libraries + client jar
             String classpath;
             if (manifest != null) {
@@ -698,17 +703,13 @@ public class LaunchCommandBuilder {
 
     /**
      * Ensure the version jar exists at versions/<versionId>/<versionId>.jar
-     * so that securejarhandler can create the "minecraft" module from it.
+     * so that securejarhandler creates module "minecraft" (from
+     * Automatic-Module-Name: minecraft) instead of "_1._20._1" (automatic
+     * module derived from filename 1.20.1.jar).
      *
-     * The version jar MUST contain SRG-mapped classes (not obfuscated Mojang
+     * Without this, findVersionJar() falls back to versions/1.20.1/1.20.1.jar
-     * names) and have Automatic-Module-Name: minecraft in its MANIFEST.MF.
+     * which produces module _1._20._1, causing split-package conflicts with
-     * Without this, securejarhandler creates an automatic module from the
+     * the minecraft module.
-     * filename, claims the net.minecraft.server.packs.resources package, but
-     * doesn't have SRG-named classes like PreparableReloadListener → crash.
-     *
-     * Priority:
-     * 1. SRG-mapped client jar from Forge libraries (client-*-srg.jar)
-     * 2. Vanilla version jar (fallback, may cause module issues)
      */
     private void ensureVersionJarForForge() throws IOException {
         String versionId = getVersionId();
@@ -719,34 +720,21 @@ public class LaunchCommandBuilder {
         Path targetJar = targetDir.resolve(versionId + ".jar");
 
         if (Files.exists(targetJar) && isValidJar(targetJar)) {
-            if (hasMinecraftModuleName(targetJar)) {
+            System.out.println(ZAnsi.green("  Version jar already exists: " + targetJar));
-                System.out.println(ZAnsi.green("  Version jar already exists with correct module name: " + targetJar));
             return;
         }
-            System.out.println(ZAnsi.yellow("  Version jar exists but missing Automatic-Module-Name: minecraft — overwriting with SRG jar"));
-            Files.delete(targetJar);
-        }
 
         Files.createDirectories(targetDir);
 
-        // Priority 1: SRG-mapped client jar from Forge libraries
+        // Copy vanilla client jar — it has Automatic-Module-Name: minecraft
-        // This jar has Automatic-Module-Name: minecraft and correct SRG class names
+        Path vanillaJar = versionsDir.resolve(mcVersion).resolve(mcVersion + ".jar");
-        Path srgJar = findSrgClientJar();
+        if (Files.exists(vanillaJar) && isValidJar(vanillaJar)) {
-        if (srgJar != null && isValidJar(srgJar)) {
+            Files.copy(vanillaJar, targetJar);
-            Files.copy(srgJar, targetJar);
+            System.out.println(ZAnsi.green("  Copied vanilla jar for securejarhandler: " + vanillaJar.getFileName() + " → " + 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)
+        System.out.println(ZAnsi.yellow("  No vanilla jar found at " + vanillaJar));
-        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.copy(sourceJar, targetJar);
-        System.out.println(ZAnsi.yellow("  Copied vanilla jar (fallback) for securejarhandler: " + sourceJar.getFileName() + " → " + targetJar));
     }
 
     /**