Fix prefix concatenation in timestamp post-processing for sensevoice (#2670)

slin000111

2025-09-20 88b464edb94531ba98744a5338965af539ab18ec

1
2
ID0012W0013 https://isv-data.oss-cn-hangzhou.aliyuncs.com/ics/MaaS/ASR/test_audio/asr_example_zh.wav
ID0012W0014 https://isv-data.oss-cn-hangzhou.aliyuncs.com/ics/MaaS/ASR/test_audio/asr_example_en.wav