Repaint the whole tree viewport while scrolling

The right-aligned icon strip is positioned against the viewport rather than
the row, so the pixels a blit scroll reuses are stale and the icons leave
ghosts behind. Scroll the viewport in simple mode, and widen every repaint
request to the full visible width so a row whose label changes size cannot
leave its icons behind either.

Also stop blacklisting an icon whose download failed only because the file
transfer channel was not up yet: channel rows are painted during connect,
well before that point, so their icons would never be retried.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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

@@ -11,6 +11,7 @@ import javax.swing.ImageIcon;
 import javax.swing.JComponent;
 import javax.swing.JScrollPane;
 import javax.swing.JTree;
+import javax.swing.JViewport;
 import javax.swing.SwingUtilities;
 import javax.swing.TransferHandler;
 import javax.swing.tree.DefaultMutableTreeNode;
@@ -96,6 +97,9 @@ public final class ServerTreePanel extends JScrollPane {
         tree.setCellRenderer(new Renderer());
         setViewportView(tree);
         getViewport().setBackground(Theme.TREE_BG);
+        // The icon strip is drawn against the viewport's right edge, so the blitted
+        // pixels a scroll would reuse are stale; repaint the whole viewport instead.
+        getViewport().setScrollMode(JViewport.SIMPLE_SCROLL_MODE);
 
         // Within the tree a drag moves the client or channel; dropped elsewhere it
         // yields the TS3 link BBCode, which the chat input accepts as plain text.
@@ -426,6 +430,17 @@ public final class ServerTreePanel extends JScrollPane {
             super(model);
         }
 
+        /**
+         * Widens every repaint request to the full visible width. Swing only asks for
+         * the row rectangle, which stops short of the right-aligned icon strip and would
+         * leave it behind when a row's label changes width.
+         */
+        @Override
+        public void repaint(long tm, int x, int y, int width, int height) {
+            Rectangle visible = getVisibleRect();
+            super.repaint(tm, visible.x, y, visible.width, height);
+        }
+
         void highlightChannel(TreePath path) {
             if (path == highlight || (path != null && path.equals(highlight))) return;
             highlight = path;