By: Michael Lynch <git@mtlynch.io>
Preserve Tinybeans GIF timing in AVIF imports The previous ffmpeg invocation let the encoder resample GIF frame timing, which collapsed source delays like 40ms and 50ms into a synthetic constant rate. Imported animated AVIFs then played at the wrong speed. Add fps_mode passthrough and a centisecond encoder time base so ffmpeg keeps Tinybeans GIF timing intact when writing animated AVIFs. Also add a unit test that locks in the ffmpeg argument list.