Map each KID to its fragments from the ciphertext moov/moof (tenc, seig, ISM duration clock) and decode up to three windows per KID that never cross into another KID, so a clear lead cannot hide a wrong key and only the failing KID is flagged. Decode every frame (wrong-key HEVC keyframes decode clean), re-judge mid-GOP starts on keyframes, time out every FFmpeg run, and refuse to store a flagged pair again in SQLite.
