fix(e2e): Fix flaky EditArticle test by waiting for Update button visibility

The test was failing intermittently because it checked button enabled state
before the article data finished loading. In some cases, the form still
showed "Publish Article" (new mode) instead of "Update Article" (edit mode).

Fix: Wait for "Update Article" button to be VISIBLE before modifying the
title. This confirms the slug is loaded and we're in edit mode. Then wait
for ENABLED state after form modifications.

Fixes timeout in EditArticle_AuthorCanModify E2E test.

Author: MCGPPeters

Abies.Conduit.E2E/ArticleTests.cs

@@ -85,13 +85,17 @@ public async Task EditArticle_AuthorCanModify()
         // Wait for the title input to have the original title (meaning article data loaded)
         await Expect(titleInput).ToHaveValueAsync(originalTitle, new() { Timeout = 10000 });
 
+        // Wait for the button to show "Update Article" (not "Publish Article") 
+        // This confirms the slug is loaded and we're in edit mode
+        var updateButton = Page.GetByRole(AriaRole.Button, new() { Name = "Update Article" });
+        await Expect(updateButton).ToBeVisibleAsync(new() { Timeout = 10000 });
+
         // Modify the title
         var newTitle = $"Updated Title {Guid.NewGuid():N}";
         await titleInput.FillAsync(newTitle);
 
-        // When editing (Slug is set), the button says "Update Article"
-        var updateButton = Page.GetByRole(AriaRole.Button, new() { Name = "Update Article" });
-        await Expect(updateButton).ToBeVisibleAsync(new() { Timeout = 5000 });
+        // Wait for the button to be enabled (form validation must pass)
+        await Expect(updateButton).ToBeEnabledAsync(new() { Timeout = 5000 });
         await updateButton.ClickAsync();
 
         // Should redirect back to article page with new title