Authors can delete their own spec comments from the spec page

Authored comments on the spec page now have a delete control in the comments action row. Selecting delete opens a Noora confirmation modal with a warning message and Cancel/Delete actions; after confirming, the comment is removed and the spec view refreshes. Only the comment’s author sees the delete option, consistent with the existing edit restriction, and the icon-only trigger matches the styling of the existing edit and permalink buttons.