Wrap the prepare_release_notes entrypoint in main(argv=None) with UTF-8
stream reconfiguration using backslashreplace error handling.
Decode release notes JSON with utf-8-sig to accept UTF-8 BOM headers.
Catch OSError and ValueError in main and report them via parser.error
rather than propagating unhandled tracebacks.
`Path.write_text(newline=...)` and `zip(strict=True)` were added in
Python 3.10. macOS ships 3.9.6 as /usr/bin/python3, the interpreter CMake
finds when no newer one is installed, so `prepare_release_notes` raised
TypeError when the release workflow wrote its notes and the
`pr_overlap_tools`, `release_package` and `linux_fixed_base` tests failed
on a stock macOS host. Writing the encoded text keeps the newline
translation off on every host, and the dynamic tag counts are compared
before the pairs are walked.
Dean