Assert edited content in open-document transition test

Agent-Logs-Url: https://github.com/PowerShell/PowerShellEditorServices/sessions/f6b6da25-a6a1-4158-9738-3a65a7e3008e

Co-authored-by: JustinGrote <15258962+JustinGrote@users.noreply.github.com>

Author: Copilot

test/PowerShellEditorServices.Test/Extensions/EditorOperationsServiceTests.cs

@@ -74,6 +74,7 @@ public void GetWorkspaceOpenDocumentsTracksEditedAndUntitledSaveStates()
                 EndOffset = 1,
                 InsertString = "Set-StrictMode -Version Latest"
             });
+            Assert.Contains("Set-StrictMode -Version Latest", openSaved.Contents, StringComparison.Ordinal);
 
             WorkspaceOpenDocument[] editedDocuments = editorOperationsService.GetWorkspaceOpenDocuments();
             Assert.Contains(editedDocuments, static document => document.Path.EndsWith("open-saved.ps1") && !document.Saved);