Validate SHA256SUMS with GNU sha256sum before publishing and advance the immutable correction release to alpha.13.
Co-authored-by: Ochenstarik <ochenstarik@inbox.ru>
Use a deterministic v1 release fixture, prepare alpha.12 version sources, and document release ownership and burned tags.
Co-authored-by: Ochenstarik <ochenstarik@inbox.ru>
alpha.10 tag produced a failed release pipeline (test-release-contract.sh
still asserted alpha.9, and run-negative-tests.sh test 5 failed on
cross-version verify-release). Per release-policy.md, published tags are
immutable — errors are fixed in the next tag.
