Review follow-ups: with retries_runaway on for an engine that also has a
trim step, a <=100-char chunk flagged as runaway raised instead of
falling back to the trimmed output that already cuts the silence+noise
tail; generate_chunked now returns the trimmed chunk in that terminal
case. ModelConfig gains aux_hf_repo_ids so /models status only reports
the Chatterbox MLX model as downloaded once mlx-community/S3TokenizerV2
is present too (matching the backend's own cache check) and
DELETE /models/{name} removes that repo as well.
Text exceeding max_chunk_chars (default 800) is automatically split at
sentence boundaries, generated per-chunk, and concatenated with a 50ms
crossfade. Works with all engines (Qwen, LuxTTS, Chatterbox, Turbo).
- Abbreviation-aware sentence splitter (Dr., Mr., e.g., decimals)
- CJK sentence-ending punctuation support
- Paralinguistic tag preservation ([laugh], [cough], etc.)
- Per-chunk seed variation to avoid correlated RNG artefacts
- Per-chunk Chatterbox trim (catches hallucination at each boundary)
- max_chunk_chars exposed as per-request param on GenerationRequest
- Text max_length raised to 50,000 characters
Closes#99
