ci: fix release asset re-upload on existing tags

gh release upload does not accept the file#label syntax (only create
does); use the bare filename in the update branch so re-tagging an
existing release refreshes its asset instead of failing.

Author: 1e1

.github/workflows/release.yml

@@ -36,12 +36,12 @@ jobs:
           GH_TOKEN: ${{ github.token }}
           TAG: ${{ github.ref_name }}
         run: |
-          ASSET="rpn-${TAG}.nwa#RPN app (${TAG}) — install via my.numworks.com/apps"
+          FILE="rpn-${TAG}.nwa"
           if gh release view "$TAG" >/dev/null 2>&1; then
             echo "Release $TAG exists — updating asset."
-            gh release upload "$TAG" "$ASSET" --clobber
+            gh release upload "$TAG" "$FILE" --clobber
           else
-            gh release create "$TAG" "$ASSET" \
+            gh release create "$TAG" "${FILE}#RPN app (${TAG}) — install via my.numworks.com/apps" \
               --title "RPN ${TAG}" \
               --notes "RPN calculator for NumWorks.