Replaces the official yt-dlp_macos sidecar. That build is PyInstaller
one-file and unpacks 37MB on every invocation, costing ~8s per call on
this machine — ruled out signing, xattrs and thinning the universal
binary as causes, and it is 8% CPU over 8s, so it is the unpack itself.
Every stream resolve paid it.
The 3MB zipapp on a trimmed portable CPython starts in ~0.45s, a 17x
improvement; a real stream resolve goes from ~10s to ~2.4s. macOS ships
only Python 3.9 and yt-dlp needs 3.10+, hence bundling an interpreter.
yt-dlp is now resolved as an argv prefix rather than a path, so a system
install (a plain script, instant) still takes precedence.
Bundle grows 153MB -> 219MB, which buys back the responsiveness.