git describe --match is a shell glob, not a regex: the trailing `*`s
in 'v[0-9]*.[0-9]*.[0-9]*' match any suffix, so a tag like
v1.2.3-checkpoint or v1.2.3-rc1 satisfied the pattern and could be
picked as LAST_TAG instead of the true last release. That silently
shifts the diff baseline and can let a push skip a required release.
--exclude '*-*' rules out any tag carrying a hyphenated suffix.
Added a regression test that tags a release-relevant change with a
v1.0.1-checkpoint tag right after v1.0.0 and asserts the gate still
fires — confirmed it fails against the pre-fix script and passes
against the fix.