Starved playback busy-spins redraws (100+/s while presenting 10)

Owner logs (2026-08-01, NAS playback of a ~160 Mbps file over a link feeding ~half that): while heavily starved, redraw rate climbs to 60-110/s against 10-17 fps presented (early intervals sit at a healthy 8-9/s). The starved path appears to re-request redraw immediately instead of pacing to the expected frame cadence - wasted CPU precisely when waiting is free. Expected: starved playback paces redraws at the frame interval (or arrival-driven), presenting late frames as they come. Numbers in the owner's session log; reproducible with any under-provisioned network share.