docs(site): mark audio.cpp SenseVoice as merged to main

[LauraGPT]

Summary

• update the bilingual audio.cpp deployment entry from candidate status to merged mainline status
• pin the install path to audio.cpp@979e070f and link the dev/main promotion evidence
• state explicitly that SenseVoice is merged to main but not yet included in a tagged audio.cpp release
• keep benchmark wording qualified to the verified hardware and workload

Validation

• python -m pytest web-pages/product-site/tests -q: 72 passed on Linux
• product-site build: 27 product pages
• product-site validation: 102 pages
• Playwright browser suite: 13/13 passed on the identical patch before push
• mobile and desktop visual inspection: no overflow
• git diff --check

Exact signed+DCO head: d1e320c0ca6f9038d35b10c78588ab5a80c8ad38.

Rollback branch: codex/backup-funasr-main-pre-audio-cpp-mainline-20260813.