Revert "fix: replace Python heredoc with shell+jq in publish.yml"

This reverts commit 9dbe10cbe7.

.github/workflows/publish.yml

@@ -32,14 +32,21 @@ jobs:
     - name: Check if build already published
       id: cdn-check
       run: |
-        SHA=$(echo "$GITHUB_SHA" | tr '[:upper:]' '[:lower:]')
-        if curl -sSf "$CDN_MANIFEST_URL" | jq -e ".builds[\"$SHA\"]" > /dev/null 2>&1; then
-          echo "Build $SHA already present on CDN; skipping."
-          echo "skip=true" >> "$GITHUB_OUTPUT"
-        else
-          echo "Build $SHA not found on CDN; continuing."
-          echo "skip=false" >> "$GITHUB_OUTPUT"
-        fi
+        set -euo pipefail
+        python3 - <<'PY'
+import json, os, urllib.request, sys
+url = os.environ["CDN_MANIFEST_URL"]
+sha = os.environ["GITHUB_SHA"].lower()
+with urllib.request.urlopen(url) as resp:
+    manifest = json.load(resp)
+exists = sha in manifest.get("builds", {})
+with open(os.environ["GITHUB_OUTPUT"], "a", encoding="utf-8") as f:
+    f.write(f"skip={'true' if exists else 'false'}\n")
+if exists:
+    print(f"Build {sha} already present on CDN; skipping packaging.")
+else:
+    print(f"Build {sha} not found on CDN; continuing.")
+PY
 
     - name: Cache NuGet packages
       uses: actions/cache@v4