G9 extension API:
  $ python3 tools/ci/check-extension-api.py --write   -> PASS: extension API surface (6 paths), EXIT=0
  $ python3 tools/ci/check-extension-api.py           -> PASS: extension API surface (6 paths), EXIT=0
  include/gufo/ext/SURFACE unchanged (git status of include/gufo/ext empty):
    # Generated by tools/ci/check-extension-api.py --write; transitive source API paths.
    include/gufo/ext/core_options.def
    include/gufo/ext/host.hpp
    include/gufo/ext/options.hpp
    include/gufo/ext/registry.hpp
    include/gufo/ext/version.hpp
    src/core/logging/logging.hpp
  => No public declaration or forwarded-surface path moved, so no ext-api label,
     no API version bump and no CHANGES.md entry is required for this card.
