Fix server management issues and improve overall stability

Major server management fixes:
- Replace Flatpak-specific pkill with universal process tree termination using pstree + process.kill()
- Fix signal format errors (SIGTERM/SIGKILL instead of TERM/KILL strings)
- Add 5-second cooldown after server stop to prevent race conditions with external detection
- Enable Stop Server button for external servers in UI
- Implement proper timeout handling with process tree killing

ContentDB improvements:
- Fix download retry logic and "closed" error by preventing concurrent zip extraction
- Implement smart root directory detection and stripping during package extraction
- Add game-specific timeout handling (8s for VoxeLibre vs 3s for simple games)

World creation fixes:
- Make world creation asynchronous to prevent browser hangs
- Add WebSocket notifications for world creation completion status

Other improvements:
- Remove excessive debug logging
- Improve error handling and user feedback throughout the application
- Clean up temporary files and unnecessary logging

🤖 Generated with [Claude Code](https://claude.ai/code)

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

public/js/server.js

@@ -115,10 +115,10 @@ function updateStatusDisplay(status) {
             statusText.textContent = 'Starting...';
         }
         
-        // For external servers, disable control buttons
+        // For external servers, allow stop but disable start/restart
         if (status.isExternal) {
             startBtn.disabled = true;
-            stopBtn.disabled = true;
+            stopBtn.disabled = false; // Allow stopping external servers
             restartBtn.disabled = true;
             consoleInputGroup.style.display = 'none';
         } else {
@@ -205,9 +205,7 @@ async function loadWorlds() {
         
         if (worlds.length === 0) {
             worldSelect.innerHTML = 
-                '<option value="">No worlds found - server will create default world</option>' +
-                '<option value="" disabled>───────────────────</option>' +
-                '<option value="" disabled>💡 Create worlds in the Worlds section</option>';
+                '<option value="" disabled>No worlds found</option>';
         } else {
             worldSelect.innerHTML = '<option value="" disabled selected>Choose a world to run</option>';
             worlds.forEach(world => {
@@ -626,4 +624,4 @@ async function downloadLogs() {
         console.error('Download logs error:', error);
         addLogEntry('error', 'Failed to download logs: ' + error.message);
     }
-}
+}