The off-air placeholder (OffAirHandler) numbers its loop floor(time()/10)
(~1.7e8) while the xc_fanout daemon restarts its own HLS counter from 0 per
stream. On an on-demand cold start a player saw the off-air sequence (~1.7e8)
then the live one (~1) — a ~10^8 BACKWARD jump, which HLS forbids, stalling
playback during warm-up.
Re-anchor the live sequence (in HLSGenerator::tokenizeDaemonPlaylist) to the
same wall-clock base via a persisted per-stream offset so it only ever
advances: it stays >= the off-air line and >= the last live window, while
still incrementing by the daemon's per-segment delta. The off-air handler is
left untouched (it is stream-agnostic). Adds HlsSequence with a pure,
unit-tested reconcile() step plus HlsSequenceTest.
