ToDo and Checklists cause ToDo buttons to vanish momentarily

As noted in [#meta2897](https://meta.trac.wordpress.org/ticket/2897) the ToDo and Checklists modules don't work together perfectly

Relevant parts of the discussion:

> However, when clicking individual checkboxes in the request, "Mark as done" button disappears, so you have to reload the page to actually mark the request as done.

> It looks like the `o2_checklist` ajax request doesn't return the meta data needed to determine a post's resolved status.
> This does get updated however with the next `o2_read` polling, so you just need to wait a few seconds rather than reload the page.

Reproduce the issue by clicking an individual checkbox in a request, then inspect the o2_checklist AJAX response and the subsequent o2_read polling behavior. Done means the “Mark as done” button remains available or updates correctly without requiring a page reload.

Written by the indexing model from the issue text.