Flatten Behavior preferences into sidebar categories and scroll to node on double-click

Behavior preferences used a nested QTreeWidget with groups like General,
Audio, Timeline, etc. Replace it with one tab per group in the left sidebar
so users can jump directly to a category without expanding a secondary menu.

Also wire double-clicking a node in the node graph to emit a selection
signal with its context, causing the parameter panel to scroll to that
node's parameters (in addition to showing/raising the panel as before).

app/widget/nodeview/nodeview.cpp

@@ -652,6 +652,10 @@ void NodeView::mouseDoubleClickEvent(QMouseEvent *event)
 										panel->setFocus(Qt::OtherFocusReason);
 				}
 			}
+
+			// Scroll the parameter editor to this node
+			emit NodeSelectionChangedWithContexts(
+				{ { item_at_cursor->GetNode(), item_at_cursor->GetContext() } });
 		}
 	}
 }