v2.4.5: Add multi-instance setting for mod developers

Allow running multiple game clients simultaneously via a new
"Allow multiple game instances" toggle in Settings. When enabled,
skips the Electron single-instance lock and the pre-launch process
kill, so existing game instances stay alive.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/managers/gameLauncher.js

@@ -30,6 +30,7 @@ const { syncModsForCurrentProfile } = require('./modManager');
 const { getUserDataPath } = require('../utils/userDataMigration');
 const { syncServerList } = require('../utils/serverListSync');
 const { killGameProcesses } = require('./gameManager');
+const { loadAllowMultiInstance } = require('../core/config');
 
 // Client patcher for custom auth server (sanasol.ws)
 let clientPatcher = null;
@@ -464,8 +465,10 @@ async function launchGame(playerNameOverride = null, progressCallback, javaPathO
   }
 
   // Kill any stalled game processes from a previous launch to prevent file locks
-  // and "game already running" issues
-  await killGameProcesses();
+  // and "game already running" issues (skip if multi-instance mode is enabled)
+  if (!loadAllowMultiInstance()) {
+    await killGameProcesses();
+  }
 
   // Remove AOT cache: generated by official Hytale JRE, incompatible with F2P JRE.
   // Client adds -XX:AOTCache when this file exists, causing classloading failures.