Core algorithms #1/#2/#3 unchanged: only entry wrapping and semaphore
source switch (injected vs self-built); build logic untouched.
- rename _build_async to public build_async (body unchanged)
- __init__ accepts keyword-only api_semaphore for cross-video sharing
- default path (no injection) is verbatim-equivalent to previous code
iomgaa
e9073bfdc2