Add MOSS-TTS-v1.5 (delay) and MOSS-Audio-Tokenizer

[ted-mosi]

What does this PR do?

This PR adds native Transformers support for:

• MossTTSDelayModel
• MossTTSDelayProcessor
• MossAudioTokenizerModel
• AutoModelForTextToWaveform
• AutoModelForAudioTokenization
• Model docs and tests for both MOSS-TTS-v1.5 (delay) and MOSS-Audio-Tokenizer

Architecture notes

MOSS-TTS-v1.5 uses a delay-pattern TTS generation format with text tokens plus multiple audio VQ channels. The processor handles user/assistant message
construction, reference-audio tokenization, delay/de-delay conversion, and waveform decoding through the native MOSS audio tokenizer.

MOSS-Audio-Tokenizer is added as a native audio-tokenizer model so MOSS-TTS no longer depends on Hub remote code for audio tokenization.

Before submitting

• I confirm that this is not a pure code agent PR.
• Did you read the contributor guideline,
  Pull Request section?
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

AI assistance disclosure

AI assistance was used while drafting and testing parts of this PR. I reviewed the changed files, checked the implementation against existing Transformers
model patterns, and ran the relevant local tests listed below. I am responsible for the final code and for responding to review feedback.

Who can review?

@eustlb @ebezzam @vasqu

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: auto, moss_audio_tokenizer, moss_tts_delay