Accepts 3.4.2 or v3.4.2; validates the tag exists on GitHub before
download, falls back to latest when omitted.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Domain arguments dropped from the quick-start command (the installer
prompts for them). English translation lives in README_EN.md, both
files cross-link.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>