Bump KVMFR to version 28 and attach generation, epoch, and deadline
identities to cadence deliveries and their timing records.
Accept phase corrections only for the exact completed publication. Keep
VM and client clocks independent by exchanging relative phase errors.
Make submission, completion, and work-estimate accounting best effort
so scheduler state cannot delay GPU submission or frame publication.
Only report the client queue lead when JIT rendering provides a valid
measurement. Clamp linear phase errors instead of wrapping them into the
opposite direction at half of a refresh period.
Timestamp OBS frames after the shared framebuffer becomes ready.
