[EW] Show "Create document" prompt when navigating to a non-existent URL

Current behavior in Experience Workspace is not matching with doc editor, navigating to a URL that doesn't correspond to an existing document triggers a prompt: "Create document or Cancel" dialog. This lets authors create new documents quickly by editing the URL directly — without going through the document library.

**Expected behavior**

When a user navigates to a URL that doesn't correspond to an existing document, EW should detect this and present a clear prompt:

- Create document — creates the document at the given path and opens it for editing
- Cancel — returns the user to their previous location or the document library

Screenshot from DA doc editor: