Checking every word of a 460-page file costs half a second, and at mount it was paid
before the document was on screen. The pass now waits for idle time (2 s timeout), as
does the one a language or dictionary change asks for; the check after an edit is
unchanged. The file is named 200 ms earlier and settles 700 ms earlier, with the same
page count, spacers, page numbers and references.