Replaces the `try/except ValueError` workaround in `_platforms.py` for checking whether a platform name is a valid Debian architecture with a direct membership check against the enum's values (`platform_name not in (arch.value for arch in DebianArchitecture)`). This works on Python 3.8+, so it no longer needs to wait for the Python 3.12 `in` behavior the old comment referenced, and makes the validation intent explicit instead of relying on exception-driven control flow. Pure refactor — no behavior change. Fixes #233