When a PDF audiobook is cast and saved to the Rehearser, page breaks now
carry the source PDF page number. In the Stage view each divider renders
as "— Page N —" instead of the generic "— Page break —".
Implementation:
- audiobook.js: `audiobookBuildScript()` encodes the page number in the
form-feed line (\fN instead of bare \f) at each page boundary.
- rehearser-parse.js: `parseScript()` now matches `line.startsWith('\f')`
and extracts the trailing page number into `line.page`.
- rehearser.js: `buildScriptPage()` renders "— Page N —" when `line.page`
is set; `toScript()` round-trips the number back (\fN) so it survives
save/reload; `importPDFScript()` also encodes page numbers (\f<pageIdx+1>)
when importing screenplay PDFs directly.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>