* fix(studio-server): keep transparency in proxies of VP8/VP9 alpha webm
A webm whose alpha lives in the VP8/VP9 side channel (alpha_mode=1,
pix_fmt yuv420p) was proxied to opaque H.264, and the VP8 proxy path
decoded it with ffmpeg's native decoder, which drops alpha. The alpha
rule and the alpha-reading decoder now live once in
@hyperframes/parsers/media-alpha, used by engine and studio-server.
* build(parsers): raise the packed size budget for the media-alpha subpath
parsers already sat at its packed budget on main; the shared alpha rule
adds 676 B of JS and 803 B of declarations (190958 B packed in CI).