Auto-editor

## Fixes
- A packet that fails to decode no longer aborts the whole analysis. The bad packet is skipped with a warning and the rest of the file is still read, so one damaged frame in a long recording can't throw away the entire result.
- Analysis now drains the decoder at the end of a stream.
- An analysis taken over skipped packets is no longer written to the cache, so holes can't be served back as real silence on later runs.
- `levels` exits non-zero when it had to skip packets. The values it did read are still printed.
- All progress and status output now goes to stderr: the progress bar, the `Finished.` line, and the progress-line clear written before a warning or error. stdout carries only data.

**Full Changelog**: https://github.com/WyattBlue/auto-editor/compare/31.7.0...31.7.2