ntpath.isreserved was added in Python 3.13, but release workflow legs
(commit-builds-summary, builds-table, builds-pending) run bare python3 on
ubuntu-24.04, whose system Python is 3.12. render-builds-table.py crashed
with AttributeError before rendering the expected-binary matrix.
Port the CPython ntpath reserved-name semantics (device stems incl.
superscript COM/LPT forms, trailing dot/space per component) into
_is_windows_reserved() in scripts/releases/r2.py so the release transport
stays self-contained on whatever python3 the runner provides. Verified
byte-parity against real ntpath.isreserved on a 239-case corpus.
4e45b78311