[Example] Add Higgs-Audio-v3 TTS example for Tesla V100 (SM70)

[jajmangold]

What

Adds a runnable real-time TTS example for bosonai/higgs-audio-v3-tts-4b on
Tesla V100 (SM70), under examples/generate/multimodal/higgs_audio_v3/:

• tts.py — the TTS driver.
• higgs_v100_low_latency.yaml — Stage-0 CUDA graph (low-latency) deploy
  profile using FLASH_ATTN_V100 + FULL_DECODE_ONLY.
• README.md — setup, requirements, and the eager baseline.

Why

Higgs-Audio-v3 already runs on V100 in eager mode, but the real-time CUDA graph
path needs two things this example documents:

• the SM70 decode CUDA graph kernel >= e64d39aa7 (already in this fork —
  earlier kernels cap the scalar-paged decode workspace at the capture-time
  seq_len and produce incorrect audio under the graph);
• the vllm-omni talker capture fix
  (vllm-project/vllm-omni#4563).

With both, Stage-0 reaches RTF ~1.0 (~2.4x faster than eager); the generated
audio transcribes back to the input prompt.

Test

Verified on a single Tesla V100: tts.py with the included config produces
correct, real-time speech.

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