Stop double-click from expanding channels in the server tree

Double-click joins a channel; expanding is left to the handles and the
keyboard.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ts3-client/swing/src/main/java/com/ts3client/ui/ServerTreePanel.java

@@ -195,6 +195,8 @@ public final class ServerTreePanel extends JPanel {
         // no expand control. Nesting is tightened too: horizontal space in this view
         // is scarce and channel names are long.
         tree.setShowsRootHandles(false);
+        // Double-click joins a channel; expanding is left to the handles and the keyboard.
+        tree.setToggleClickCount(0);
         if (tree.getUI() instanceof BasicTreeUI) {
             BasicTreeUI ui = (BasicTreeUI) tree.getUI();
             ui.setLeftChildIndent(4);