pfx 0.25.3

pfx 0.25.3

• System ffmpeg. Both kinds of render (pfx render and the asset clips) now encode with the ffmpeg on PATH instead of downloading and unpacking a pinned archive into the machine cache. Install your system's ffmpeg with libx264 and zscale; ffmpeg 9 or later is recommended, since earlier releases write no colour range into the ProRes alpha master. Manifests record the ffmpeg used as {path, version, sha256} in place of the archive's url and sha256. crates/run/render.toml keeps only the moved dependencies, and pfx-run no longer depends on ureq or toml. An old ffmpeg/ folder in the cache is still listed by pfx cache and pfx cache --prune drops it once it has gone unused for 30 days.
• Pacing. The timing a paced slice hands to the next Turns::add is now kept per thread, so pacers on different threads no longer classify each other's adds.
• CI runs on Ubuntu 26.04 with the system ffmpeg installed.