normalize_text() handles three Whisper quirks that produced messy F5
ref_texts:
1. Lowercase output with no terminal period — capitalize first letter,
append "." if missing.
2. Hallucinated "' clusters Whisper inserts when it interprets a
fragment as quoted dialogue (cora, ivan, atlas, hope had these).
Strip everywhere; never legitimate English punctuation.
3. Trailing apostrophe-then-period (.'.) from earlier rounds where a
closing-quoted line got an extra "." appended — collapse to single
terminal. Function is now idempotent.
Adds --from-cache flag: skip ASR, re-apply normalize from cached
whisper_refs.json. No GPU needed, useful after tuning the normalizer.
Lazy-imports torch so --from-cache works on any host.
Affects 9 of 40 voices: clara, grace, hazel, iris, felix, hugo
(lowercase fix); cora, ivan, atlas, hope (quote-cluster fix).
Previous ref_texts were LibriSpeech dataset labels (ALL CAPS, no
punctuation). F5-TTS conditions on ref_text to align reference audio
prosody — commas, periods, casing matter. Now using whisper-large-v3
transcripts of the actual cloned-voices/*.wav files.
Generated via: make whisper-refs (on a GPU host).
Affects all 40 voices in both tts-1-f5 and tts-1-qwen engine blocks.
Sidecar cloned-voices/whisper_refs.json kept for traceability.
