fix: lockfile workflow opens PR on dev instead of direct push

dev is a protected branch requiring PRs. The previous direct push caused
the lockfile update CI job to fail with 'protected branch hook declined'.
When the triggering branch is dev, the workflow now creates a side branch
and opens a PR; all other branches continue to push directly.

.github/workflows/update-lockfile.yml

@@ -15,6 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
       contents: write
+      pull-requests: write
     steps:
       - name: Checkout repository
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
@@ -39,9 +40,24 @@ jobs:
 
       - name: Commit and push updated lockfile
         if: steps.diff.outputs.changed == 'true'
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           git config user.name "github-actions[bot]"
           git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
           git add uv.lock
           git commit -m "chore: update lockfile"
+
+          if [ "$GITHUB_REF_NAME" = "dev" ]; then
+            # dev is protected — open a PR rather than pushing directly
+            BRANCH="chore/lockfile-$(git rev-parse --short HEAD)"
+            git checkout -b "$BRANCH"
+            git push origin "$BRANCH"
+            gh pr create \
+              --base dev \
+              --head "$BRANCH" \
+              --title "chore: update lockfile" \
+              --body "Automated lockfile update triggered by a \`pyproject.toml\` change on \`dev\`."
+          else
             git push
+          fi