State explicitly in the README and download page that the
platform-specific prebuilt files are standalone executables, not
archives. Include the rename and executable-permission step for macOS
and Linux in the README.
Addresses #2956. Source archives are not described as executables.
Validation: the official `docs/build_website.py` completed and the
generated download page contains the new guidance. Used a Python venv
with the site's required rendering packages; restored the Windows
checkout's manual symlink in a temporary build copy only. jq itself was
not built or tested for this documentation-only change.
Co-authored-by: Hugohong258 <[email protected]>
Hugohong258