SCIENTIFIC INTEGRITY: Tests now retry transient errors (429, 5xx,
timeouts) with exponential backoff instead of falsely passing.
Prior to this fix, ~35% of 'passing' tests were masked failures.
Now tests will PASS (verified), FAIL (couldn't verify), or SKIP.
- Add `un languages [--json]` command to list available execution languages
- Add `un image` command with full image management:
- --list, --info, --delete, --lock, --unlock
- --publish, --visibility, --spawn, --clone
- Update CLI_SPEC.md with new command documentation
- All implementations follow consistent patterns