SFV checksum verification files are legitimately tiny (~128 bytes) but were
rejected by the "suspicious small download" detection, causing infinite
"Direktlink erneuern" retry loops that blocked package extraction.
- Add KNOWN_SMALL_FILE_RE for .sfv, .nfo, .nzb, .md5, .sha1, .sha256, .crc,
.txt, .url, .lnk, .srr file extensions
- Skip suspicious-small-download rejection for known small files when they
match their expected size (or have no size expectation)
- Skip tiny-download error detection for known small metadata files
- Add test: verifies .sfv file downloads without retries and completes
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
