The idea of Special:ShowEntity is to provide a way to link to local pages without knowing the local title, when knowing the item ID.
Special:ShowEntity takes an entity ID as a parameter (optionally using subpage syntax). If the entity is connected to a local page, Special:ShowEntity can (optionally?) forward to that page. Otherwise, it should show the following:
* label and description, plus a link to the entity on the repo
* sitelinks (in the sidebar, or a more prominent location?)
* A "create page" button, with an input field for the desired title, pre-populated with the entity's label. (Items only?)
The behavior of the "create page" button should be:
* fail if a page with that title already exists
* forward to an empty edit form for the desired page; the page is only created when the edit form is filled in and saved.