ci: regenerate yarn.lock as part of the changesets version-bump step (#52)

* ci: regenerate yarn.lock as part of the changesets version-bump step

yarn changeset version only rewrites package.json/CHANGELOG.md, never
re-runs install. When it bumps a dependent's peerDependency range
(e.g. common-cse-machine >=0.1.0 -> >=0.2.0 in runner/web-cse-machine),
that leaves yarn.lock stale, which then fails the resulting "Version
Packages" PR's immutable install in CI (exactly what happened on #51).

Chain a plain "yarn install" after "yarn changeset version" so the
lockfile is always in sync in the same bot commit. It's a no-op when
nothing needs to change.

* ci: set YARN_ENABLE_IMMUTABLE_INSTALLS=false for the version-bump install

Matches changesets/action's own documented recommendation for the
"run yarn install after changeset version" pattern (see its README's
Yarn section) — without it this install could itself run in an
immutable/frozen mode and fail instead of doing its job.

Author: Akshay-2007-1

.github/workflows/on_push.yml

@@ -33,9 +33,19 @@ jobs:
         uses: changesets/action@v1
         with:
           publish: yarn changeset publish
-          version: yarn changeset version
+          # changeset version only rewrites package.json/CHANGELOG.md — it never re-runs
+          # install, so a peerDependency range bump (e.g. common-cse-machine >=0.1.0 -> >=0.2.0
+          # in a dependent's package.json) can leave yarn.lock stale. That stale lockfile then
+          # fails CI's immutable install on the resulting "Version Packages" PR. Re-running
+          # install here keeps the lockfile in sync in the same commit; it's a no-op when
+          # nothing changed.
+          version: yarn changeset version && yarn install
         env:
           NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+          # changesets/action's own README recommends this for the yarn-install-after-version
+          # pattern: without it, this install could itself run in an immutable/frozen mode and
+          # fail instead of regenerating the lockfile.
+          YARN_ENABLE_IMMUTABLE_INSTALLS: false
       - name: Upload artifacts
         id: deployment
         uses: actions/upload-pages-artifact@v5