Add tests for important orchestrator edge cases:
- Nested archives (zip-inside-zip): verifies multi-round extraction
discovers archives within previously-extracted archives
- Context cancellation: graceful handling without hanging
- Multiple archives at same level: both extracted in one round
- Corrupt archive: skipped without error, doesn't block other work
- Empty archive: not counted as extracted
- Per-archive file limit: partial extraction handled correctly
- Relationship structure: contains relationships emit the archive's
coordinates as the source side
Signed-off-by: Thomas Bechtold <thomasbechtold@jpberlin.de>