ci: amend openclaw build into trigger commit instead of separate commit

Avoids extra bot commits that cause push rejections. Uses --amend
and --force-with-lease so dist/openclaw changes fold into the
original commit cleanly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/build-openclaw.yml

@@ -37,6 +37,6 @@ jobs:
           if git diff --cached --quiet; then
             echo "No changes to commit"
           else
-            git commit -m "chore: rebuild dist/openclaw from source"
-            git push
+            git commit --amend --no-edit
+            git push --force-with-lease
           fi