fix(ci): delete local tags before creating nightly release (#218)

The nightly workflow fails when re-running on the same day because
after deleting the remote tag, the local tag still exists in the
runner's checkout. GitHub CLI sees this local tag and expects it
to be pushed to remote.

This fix adds 'git tag -d' to delete local tags in both the
cleanup and create release steps, ensuring clean state before
creating new releases.

.github/workflows/nightly.yml

@@ -100,6 +100,7 @@ jobs:
                 echo "Deleting old nightly release: $tag (created: $(date -d @$RELEASE_DATE -u +"%Y-%m-%d %H:%M:%S UTC"))"
                 gh release delete "$tag" --yes --repo ${{ github.repository }} 2>/dev/null || true
                 git push origin :refs/tags/"$tag" 2>/dev/null || true
+                git tag -d "$tag" 2>/dev/null || true
               else
                 echo "Keeping nightly release: $tag (created: $(date -d @$RELEASE_DATE -u +"%Y-%m-%d %H:%M:%S UTC"))"
               fi
@@ -210,6 +211,7 @@ jobs:
           # If a release for today already exists, delete it first
           gh release delete "$RELEASE_TAG" --yes --repo ${{ github.repository }} 2>/dev/null || true
           git push origin :refs/tags/"$RELEASE_TAG" 2>/dev/null || true
+          git tag -d "$RELEASE_TAG" 2>/dev/null || true
           
           gh release create "$RELEASE_TAG" \
             --title "Nightly Build - ${{ steps.version.outputs.version }}" \