docs: complete winget coverage, normalise install headings

- README_pt.md: add the winget section (only translation missing it)
- docs/guide/getting-started/installation.md: add winget install and
  uninstall entries
- README_{es,fr,ja,ko,zh}.md: drop the superlative from the winget
  heading so all seven READMEs read "winget (Windows)", matching the
  existing "Homebrew (recommended)" convention
- README.md: shorten the Native Windows heading to "(manual install)",
  move the winget pointer into prose

Deliberately out of scope: docs/guide/getting-started/installation.md
still tells Windows users to use WSL "for full hook support". README.md
contradicts this - native Windows hooks have worked since v0.37.2.
Correcting it means rewriting text this PR does not otherwise touch, so
it is left for a separate change.