Fix flaky Navigation focus mode test (#57016)

* Add missing assertion

* Test expect url

* Do setup before entering editor

test/e2e/specs/site-editor/navigation-editor.spec.js

@@ -20,20 +20,6 @@ test.describe( 'Editing Navigation Menus', () => {
 		editor,
 	} ) => {
 		await test.step( 'Manually browse to focus mode for a Navigation Menu', async () => {
-			// We could Navigate directly to editing the Navigation Menu but we intentionally do not do this.
-			//
-			// Why? To provide coverage for a bug that caused the Navigation Editor behaviours to fail
-			// only when navigating through the editor screens (rather than going directly to the editor by URL).
-			// See: https://github.com/WordPress/gutenberg/pull/56856.
-			//
-			// Example (what we could do):
-			// await admin.visitSiteEditor( {
-			// 	postId: createdMenu?.id,
-			// 	postType: 'wp_navigation',
-			// } );
-			//
-			await admin.visitSiteEditor();
-
 			// create a Navigation Menu called "Test Menu" using the REST API helpers
 			const createdMenu = await requestUtils.createNavigationMenu( {
 				title: 'Primary Menu',
@@ -48,6 +34,20 @@ test.describe( 'Editing Navigation Menus', () => {
 					'<!-- wp:navigation-link {"label":"Another Item","type":"custom","url":"http://www.wordpress.org/","kind":"custom"} /-->',
 			} );
 
+			// We could Navigate directly to editing the Navigation Menu but we intentionally do not do this.
+			//
+			// Why? To provide coverage for a bug that caused the Navigation Editor behaviours to fail
+			// only when navigating through the editor screens (rather than going directly to the editor by URL).
+			// See: https://github.com/WordPress/gutenberg/pull/56856.
+			//
+			// Example (what we could do):
+			// await admin.visitSiteEditor( {
+			// 	postId: createdMenu?.id,
+			// 	postType: 'wp_navigation',
+			// } );
+			//
+			await admin.visitSiteEditor();
+
 			const editorSidebar = page.getByRole( 'region', {
 				name: 'Navigation',
 			} );
@@ -66,6 +66,10 @@ test.describe( 'Editing Navigation Menus', () => {
 				} )
 			).toBeVisible();
 
+			await expect( page ).toHaveURL(
+				`wp-admin/site-editor.php?path=%2Fnavigation`
+			);
+
 			await editorSidebar
 				.getByRole( 'button', {
 					name: 'Primary Menu',
@@ -77,10 +81,12 @@ test.describe( 'Editing Navigation Menus', () => {
 			);
 
 			// Wait for list of Navigations to appear.
-			editorSidebar.getByRole( 'heading', {
-				name: 'Primary Menu',
-				level: 1,
-			} );
+			await expect(
+				editorSidebar.getByRole( 'heading', {
+					name: 'Primary Menu',
+					level: 1,
+				} )
+			).toBeVisible();
 
 			// Switch to editing the Navigation Menu
 			await editorSidebar