Strip leading v from release tag before passing as version

The release tag (e.g. v2026.1) was passed verbatim to
generate_release_artifacts.py, which validates against YYYY.MICRO and
rejected the v prefix. Derive a tag-less VERSION for the build action
and artifact filenames; keep the original TAG only where it identifies
the GitHub release itself.

Author: pelson

.github/workflows/release.yml

@@ -17,17 +17,26 @@ jobs:
         with:
           ref: ${{ github.event.release.tag_name }}
 
+      - name: Derive version from release tag
+        id: version
+        run: echo "value=${TAG#v}" >> "$GITHUB_OUTPUT"
+        env:
+          TAG: ${{ github.event.release.tag_name }}
+
       - uses: ./.github/actions/build-font
         with:
-          version: ${{ github.event.release.tag_name }}
+          version: ${{ steps.version.outputs.value }}
           push-image: 'true'
 
       - name: Upload assets to the release
+        env:
+          TAG: ${{ github.event.release.tag_name }}
+          VERSION: ${{ steps.version.outputs.value }}
         run: |
-          gh release upload "${{ github.event.release.tag_name }}" \
-            dist/xkcd-script-${{ github.event.release.tag_name }}.otf \
-            dist/xkcd-script-${{ github.event.release.tag_name }}.ttf \
-            dist/xkcd-script-${{ github.event.release.tag_name }}.woff \
-            dist/xkcd-script-${{ github.event.release.tag_name }}.woff2 \
-            dist/xkcd-mathjax3-${{ github.event.release.tag_name }}.js \
+          gh release upload "$TAG" \
+            "dist/xkcd-script-${VERSION}.otf" \
+            "dist/xkcd-script-${VERSION}.ttf" \
+            "dist/xkcd-script-${VERSION}.woff" \
+            "dist/xkcd-script-${VERSION}.woff2" \
+            "dist/xkcd-mathjax3-${VERSION}.js" \
             --clobber