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.
Built-in 64's slot-0 operand is a symbol-table-1 type-6 message id, and every
one of them now has caption text: 2683 of 2683 call sites across the 28 stage
scripts, 1338 distinct names, no residue of any kind.
This only became reachable once build_caption_text was switched to the IXUD
field table (537 -> 8800 lines); before that most of these names had nothing
to resolve to.
Adds isl_dialogue.py plus a committed Stage 02 sample. Does not settle which
recording plays for a given line, multi-page captions, or the other five
languages.
