attempt to fix incorrect page number in table of contents when footer pushes section to the next page

[DetachHead]

fixes #1120

i'm still trying to figure out what the fix is. i think my attempt here is at least partially correct, as it now creates an entry for both the wrong page number and the correct one:

i'm trying to just delay the rendering of the table of contents until after the correct page numbers for each section have been determined. i tried wrapping TableOfContent in a DelayedWidget but that didn't seem to have any effect. any guidance would be appreciated, thanks