Read-only pre-flight verification of a staged release candidate (RC) for `<upstream>`. Checks artefact integrity (GPG signatures and checksums), Apache RAT licence headers, NOTICE/LICENSE completeness, prohibited-binary absence (including `.pyc` / `__pycache__`), source-tree integrity (no dangling s
Read-only pre-flight verification of a staged release candidate (RC) for `<upstream>`. Checks artefact integrity (GPG signatures and checksums), Apache RAT licence headers, NOTICE/LICENSE completeness, prohibited-binary absence (including `.pyc` / `__pycache__`), source-tree integrity (no dangling symlinks or broken internal references), and version-string consistency. Emits a structured PASS / PA