fix(release): prevent duplicate incomplete agent notifications

.github/workflows/agents-release.yml

@@ -455,6 +455,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           token: ${{ steps.release-token.outputs.token }}
+          fetch-depth: 0
       - uses: actions/download-artifact@v4
         with:
           path: artifacts
@@ -652,6 +653,9 @@ jobs:
           PREV_VERSIONS: ${{ needs.bump-versions.outputs.prev_versions }}
           PREV_TAG: ${{ needs.bump-versions.outputs.prev_tag }}
         run: |
+          set -euo pipefail
+          git rev-parse --verify "${PREV_TAG}^{commit}" > /dev/null
+
           NOTES=""
           DRIVER_NAMES=()
           module_names() {