Measured the <id>_<page>_<line> key structure: a page is one subtitle box of
3 or 4 wrapped lines, and successive pages are successive utterances by
possibly different speakers. 452 of 4091 ids span more than one page, up to 8.
That refutes the isl_dialogue.py committed two commits ago, which read only
page 000 -- 356 of the 1338 script message names are multi-page, so a quarter
of its output was truncated to the opening utterance. Tool now walks pages
until one is empty; Stage 02 sample regenerated (43 of 213 calls multi-page).
The 2683/2683 resolution figure is unaffected: it counted ids that have text,
and every id does have a page 000. What was wrong was the rendered text.
66c3551a95