Fail the tag-existence check on ls-remote errors

Captures the ls-remote output first so a transient failure aborts the run
instead of being read as "tag absent".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: jasonvarga

.github/workflows/release.yml

@@ -52,10 +52,8 @@ jobs:
 
       - name: Assert tag does not already exist
         run: |
-          if git ls-remote --tags origin "$TAG" | grep -q .; then
-            echo "::error::Tag $TAG already exists on remote. Aborting."
-            exit 1
-          fi
+          existing="$(git ls-remote --tags origin "$TAG")"
+          [ -z "$existing" ] || { echo "::error::Tag $TAG already exists on remote. Aborting."; exit 1; }
 
       - name: Use Node.js 20.19.0
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0