Previously, switching to the release channel would delete .git/ and
fall back to a ZIP download. This broke update.bat, manual git
commands, and CM git-based update detection.
Now the release path uses git checkout <latest-tag> when .git exists,
and only falls back to ZIP when .git is absent (CM CNR installs).
.git is never deleted - the ZIP→nightly path remains a one-way
upgrade via _init_git_repo.
Also updates locale strings (en, zh-CN, zh-TW, ja) to remove the
now-inaccurate "remove the Git repository" wording.
Will Miao
b464fdc333