Add test_python_floor to the containerized packaging matrix:
- Sub-check 1: Ubuntu 22.04 (Python 3.10) installs successfully,
confirming the floor is met on the oldest supported deb target.
- Sub-check 2: Debian 11 (Python 3.9) fails to configure due to
unmet python3 (>= 3.10) dependency, verifying clean failure below floor.
Fix Makefile check-python gate to enforce Python >= 3.10, matching the
nfpm depends declaration.
Full compatibility matrix is now green: 17 packaging tests (dormant
install, migration guard, upgrade semantics, removal semantics, and
Python floor) pass across all four targets (Debian 12, Ubuntu 22.04,
Ubuntu 24.04, Fedora 40).
Co-authored-by: CommandCodeBot <noreply@commandcode.ai>