[Feat][Qwen3TTS] reduce TTFA with flexible initial phase (#1583)

Signed-off-by: pablo <pablo@agigo.ai>
Co-authored-by: pablo <pablo@agigo.ai>

docs/user_guide/examples/offline_inference/qwen3_tts.md

@@ -98,7 +98,8 @@ Add `--streaming` to stream audio chunks progressively via `AsyncOmni` (requires
 python end2end.py --query-type CustomVoice --streaming --output-dir /tmp/out_stream
 ```
 
-Each 25-frame Code2Wav chunk is logged as it arrives. The final WAV file is written once generation
+Each Code2Wav chunk is logged as it arrives (default 25 frames; configurable via `codec_chunk_frames`
+and `initial_codec_chunk_frames` in the stage config). The final WAV file is written once generation
 completes. This demonstrates that audio data is available progressively rather than only at the end.
 
 > **Note:** Streaming uses `AsyncOmni` internally. The non-streaming path (`Omni`) is unchanged.

docs/user_guide/examples/online_serving/qwen3_tts.md

@@ -268,7 +268,7 @@ Returns binary audio data with appropriate `Content-Type` header (e.g., `audio/w
 ## Streaming
 
 Set `stream=true` with `response_format="pcm"` to receive raw PCM audio chunks as they are decoded
-(one chunk per 25-frame Code2Wav window):
+(one chunk per Code2Wav window, default 25 frames; configurable in the stage config):
 
 ```bash
 curl -X POST http://localhost:8091/v1/audio/speech \