Extracts the mpv.MPV() kwargs into a Qt-free pure function so the
security-relevant options can be unit-tested on CI (which lacks
PySide6 and libmpv). The builder embeds the audit #2 hardening —
ytdl="no", load_scripts="no", and a lavf protocol whitelist of
file,http,https,tls,tcp — alongside the existing playback tuning.
Not yet wired into _MpvGLWidget; that lands in the next commit.
Audit-Ref: SECURITY_AUDIT.md finding #2
Severity: High