A video in the library (an MP4 or MOV from a Lightroom catalog import) went
to the image decoders for its grid thumbnail, failed with "unrecognised
image format", showed a "!" and was tried again whenever the library
changed (issue #2682: four of its six undecodable files were healthy
videos). Photo::is_video recognises a video by its kind, by the format
VIDEO a Lightroom catalog gives it (its import still keeps them as images),
or by its extension; Session::thumb_job returns None for one, so the grid,
filmstrip, Compare and Build Previews ask for no thumbnail. The cell keeps
its plain placeholder.
Tests: model::edited_tests::a_video_is_known_by_its_kind_format_or_extension,
render::thumbnail_tests::a_video_asks_the_decoders_for_no_thumbnail (fails
on main: a job is built for the video).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
