Add Volcengine support for TTS and ASR services

- Introduced Volcengine as a new provider for both TTS and ASR services.
- Updated configuration files to include Volcengine-specific parameters such as app_id, resource_id, and uid.
- Enhanced the ASR service to support streaming mode with Volcengine's API.
- Modified existing tests to validate the integration of Volcengine services.
- Updated documentation to reflect the addition of Volcengine as a supported provider for TTS and ASR.
- Refactored service factory to accommodate Volcengine alongside existing providers.

engine/config/agents/example.yaml

@@ -21,12 +21,17 @@ agent:
     api_url: https://api.qnaigc.com/v1
 
   tts:
-    # provider: openai_compatible | siliconflow | dashscope
+    # provider: openai_compatible | siliconflow | dashscope | volcengine
     # dashscope defaults (if omitted):
     #   api_url: wss://dashscope.aliyuncs.com/api-ws/v1/realtime
     #   model: qwen3-tts-flash-realtime
     #   dashscope_mode: commit (engine splits) | server_commit (dashscope splits)
     #   note: dashscope_mode/mode is ONLY used when provider=dashscope.
+    # volcengine defaults (if omitted):
+    #   api_url: https://openspeech.bytedance.com/api/v3/tts/unidirectional
+    #   resource_id: seed-tts-2.0
+    #   app_id: your volcengine app key
+    #   api_key: your volcengine access key
     provider: openai_compatible
     api_key: your_tts_api_key
     api_url: https://api.siliconflow.cn/v1/audio/speech
@@ -35,11 +40,21 @@ agent:
     speed: 1.0
 
   asr:
-    # provider: buffered | openai_compatible | siliconflow | dashscope
+    # provider: buffered | openai_compatible | siliconflow | dashscope | volcengine
     # dashscope defaults (if omitted):
     #   api_url: wss://dashscope.aliyuncs.com/api-ws/v1/realtime
     #   model: qwen3-asr-flash-realtime
     #   note: dashscope uses streaming ASR mode (chunk-by-chunk).
+    # volcengine defaults (if omitted):
+    #   api_url: wss://openspeech.bytedance.com/api/v3/sauc/bigmodel
+    #   model: bigmodel
+    #   resource_id: volc.bigasr.sauc.duration
+    #   app_id: your volcengine app key
+    #   api_key: your volcengine access key
+    #   request_params:
+    #     end_window_size: 800
+    #     force_to_speech_time: 1000
+    #   note: volcengine uses streaming ASR mode (chunk-by-chunk).
     provider: openai_compatible
     api_key: you_asr_api_key
     api_url: https://api.siliconflow.cn/v1/audio/transcriptions