Adds a TTS read-along to the book reader. Tap the play button in the
toolbar; AVSpeechSynthesizer reads the chapter paragraph-by-paragraph
with the current word highlighted in yellow, auto-scrolling the active
paragraph to centre. Tap any word during read-along to pause and open
the definition sheet; reading resumes when the sheet dismisses.
Behavior per spec:
- Tap-to-define interrupts the synth (pauseSpeaking at: .immediate) and
resumes on sheet dismiss.
- Voice picker sheet (waveform.circle toolbar button) lists installed
Spanish voices grouped by Premium / Enhanced / Default quality, with
a "Download more voices…" row that opens iOS Settings (no public
deep-link to Accessibility → Spoken Content exists; the footer spells
out the path).
- Speed picker (Slow / Normal / Fast) drives AVSpeechUtterance.rate.
- Stops at chapter end, no auto-advance to the next chapter.
- Vocabulary lines shaped `palabra = meaning` are skipped — the synth
would otherwise say "palabra equals meaning" and they're reference
material, not prose.
Audio session uses .playback + .spokenAudio mode and is properly
deactivated with .notifyOthersOnDeactivation on stop() so music apps
resume cleanly after reading ends.
Voice/rate persisted via @AppStorage; controller picks them up
onAppear and writes back through Bindings the picker mutates.
Word-index space in BookSpeechController.wordRanges(in:) matches
BookReaderView's split(separator: " ") rendering exactly — both split
on ASCII U+0020 only, so willSpeakRange callbacks resolve to the right
visible word.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Trey T
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