Add inspector tree left/right keyboard navigation coverage

Updates inspector tree tests to cover left and right arrow navigation, including expand, next-row selection, and parent selection behavior. Also ensures left navigation to a parent notifies Flutter Inspector consistently with other keyboard selection changes.

Author: muhammadkamel

packages/devtools_app/lib/src/screens/inspector/inspector_tree_controller.dart

@@ -357,7 +357,10 @@ class InspectorTreeController extends DisposableController
           return true;
         }
         if (selectionLocal.parent != null) {
-          return setSelectedNode(selectionLocal.parent);
+          return setSelectedNode(
+            selectionLocal.parent,
+            notifyFlutterInspector: true,
+          );
         }
         return false;
       },

packages/devtools_app/test/screens/inspector/inspector_tree_test.dart

@@ -196,6 +196,66 @@ void main() {
         expect(capturedNotify, isTrue);
       },
     );
+
+    testWidgets(
+      'navigateRight triggers onSelectionChange with notifyFlutterInspector true',
+      (WidgetTester tester) async {
+        bool? capturedNotify;
+        final treeController = buildTreeController(
+          onSelectionChange: ({bool notifyFlutterInspector = false}) {
+            capturedNotify = notifyFlutterInspector;
+          },
+        );
+
+        await pumpInspectorTree(tester, treeController: treeController);
+
+        final root = treeController.root!;
+        final firstChild = root.children.first;
+        root.isExpanded = false;
+        treeController.setSelectedNode(root);
+
+        // First right-arrow navigation expands the selected node.
+        capturedNotify = null;
+        treeController.navigateRight();
+        await tester.pump();
+
+        expect(root.isExpanded, isTrue);
+        expect(treeController.selection, root);
+        expect(capturedNotify, isNull);
+
+        // Once expanded, right-arrow navigation selects the next visible row.
+        treeController.navigateRight();
+        await tester.pump();
+
+        expect(treeController.selection, firstChild);
+        expect(capturedNotify, isTrue);
+      },
+    );
+
+    testWidgets(
+      'navigateLeft triggers onSelectionChange with notifyFlutterInspector true',
+      (WidgetTester tester) async {
+        bool? capturedNotify;
+        final treeController = buildTreeController(
+          onSelectionChange: ({bool notifyFlutterInspector = false}) {
+            capturedNotify = notifyFlutterInspector;
+          },
+        );
+
+        await pumpInspectorTree(tester, treeController: treeController);
+
+        final root = treeController.root!;
+        final firstChild = root.children.first..isExpanded = false;
+        treeController.setSelectedNode(firstChild);
+
+        capturedNotify = null;
+        treeController.navigateLeft();
+        await tester.pump();
+
+        expect(treeController.selection, root);
+        expect(capturedNotify, isTrue);
+      },
+    );
   });
 
   group('InspectorTree keyboard events', () {
@@ -243,5 +303,65 @@ void main() {
         expect(capturedNotify, isTrue);
       },
     );
+
+    testWidgets(
+      'arrowRight key triggers onSelectionChange with notifyFlutterInspector true',
+      (WidgetTester tester) async {
+        bool? capturedNotify;
+        final treeController = buildTreeController(
+          onSelectionChange: ({bool notifyFlutterInspector = false}) {
+            capturedNotify = notifyFlutterInspector;
+          },
+        );
+
+        await pumpInspectorTree(tester, treeController: treeController);
+
+        final root = treeController.root!;
+        final firstChild = root.children.first;
+        root.isExpanded = false;
+        treeController.setSelectedNode(root);
+
+        // First arrowRight expands the selected node.
+        capturedNotify = null;
+        await tester.sendKeyEvent(LogicalKeyboardKey.arrowRight);
+        await tester.pump();
+
+        expect(root.isExpanded, isTrue);
+        expect(treeController.selection, root);
+        expect(capturedNotify, isNull);
+
+        // Once expanded, arrowRight selects the next visible row.
+        await tester.sendKeyEvent(LogicalKeyboardKey.arrowRight);
+        await tester.pump();
+
+        expect(treeController.selection, firstChild);
+        expect(capturedNotify, isTrue);
+      },
+    );
+
+    testWidgets(
+      'arrowLeft key triggers onSelectionChange with notifyFlutterInspector true',
+      (WidgetTester tester) async {
+        bool? capturedNotify;
+        final treeController = buildTreeController(
+          onSelectionChange: ({bool notifyFlutterInspector = false}) {
+            capturedNotify = notifyFlutterInspector;
+          },
+        );
+
+        await pumpInspectorTree(tester, treeController: treeController);
+
+        final root = treeController.root!;
+        final firstChild = root.children.first..isExpanded = false;
+        treeController.setSelectedNode(firstChild);
+
+        capturedNotify = null;
+        await tester.sendKeyEvent(LogicalKeyboardKey.arrowLeft);
+        await tester.pump();
+
+        expect(treeController.selection, root);
+        expect(capturedNotify, isTrue);
+      },
+    );
   });
 }