v0.1.1

Extract the version-rewrite/verify logic into .github/set-version.sh

The release job's commit-back step duplicated the build job's rewrite
awk verbatim but had no guard: if main's Cargo.toml ever drifted from
the expected format, the rewrite would silently no-op, and
`git commit --allow-empty` + push would still succeed, leaving a green
job that bumped nothing. Moving the rewrite and the guard into one
script both jobs call closes that gap and removes the duplication that
let it happen in the first place.