New dev-dependency-only crate crates/testkit (L0, no FilmCraft deps):
FILMCRAFT_FFMPEG/FILMCRAFT_FFPROBE, then PATH (incl. .exe), then known
dirs; SKIPPED lines and FILMCRAFT_REQUIRE_ORACLES=1 to make skips fail;
require_ffmpeg!/require_ffprobe!/require_oracles!; fixtures_dir() under
<workspace>/target/fixtures with per-thread temp names and atomic
generation. Oracle helpers in aac, opus, h264, hevc, h264enc, isobmff,
matroska, prores and export migrated (codecs left on its local lookup).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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