The delayed-HLS branch inline-computed two things: the resume segment number
parsed from the existing delay playlist (last-or-previous line's _<n>.ts index),
and the delay sleep seconds (delay_minutes*60 reduced ~10s per already-produced
segment, floored at 0). Pull both into pure resolveDelaySegmentStart() and
resolveDelaySleepTime() helpers with unit tests. The playlist merge and the
short-playlist abort stay inline. No behaviour change.
Verified: phpstan level 5 green, phpunit 391/391, make gates green.