Two failures from today's library run, both caught, both now handled:
1. The picture gate compared frames by INDEX after an input seek. A seek snaps to a keyframe, and
it snapped to a DIFFERENT keyframe for the source and for the encode - measured: two 1500-frame
decodes whose start times differed by ~10 s, so every frame met the wrong one and a perfectly
good encode scored min SSIM 0.25 (and a file with a hole in its source's timeline scored 0.45).
The window is now cut with the trim filter on absolute PTS (-copyts), so both sides cover
exactly the same interval no matter where the seek lands; a self-comparison then measures
lo=1.0/mean=1.0 (validated), and a frame-count difference >1% is reported as 'gate NOT
APPLICABLE' rather than failing a file whose source is simply missing frames.
2. RaiDrive/Dokan returned from a 403 MB write with NO error while the remote file held 12.5 MB,
and surfaced 'the operation didn't complete within specific time limit' afterwards. The
SHA-256 read-back caught it (nothing was replaced), and it now retries the upload instead of
failing outright. Uploads use 4 MB chunks with a periodic flush; source copies retry 5x with a
longer backoff and smaller chunks.