Fix version bump race condition with pull before push

When multiple labels are added simultaneously, multiple workflow runs
can trigger. Add git pull --rebase before push to handle concurrent
commits from parallel workflow runs.

This prevents push failures when another workflow instance has already
pushed changes to the PR branch.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: kompre

.github/workflows/version-bump.yml

@@ -99,6 +99,11 @@ jobs:
             echo "No changes to commit"
           else
             git commit -m "Bump version to ${{ steps.bump.outputs.new_version }} [skip ci]"
+
+            # Pull with rebase in case another workflow pushed
+            git pull --rebase origin ${{ github.head_ref }}
+
+            # Push changes
             git push
           fi