Fix actionlint install in CI workflow

The download URL was missing the version number in the asset filename.
Use the official download script which handles version resolution.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
           persist-credentials: false
       - name: Install actionlint
         run: |
-          curl -sL https://github.com/rhysd/actionlint/releases/latest/download/actionlint_linux_amd64.tar.gz | tar xz
+          bash <(curl -sL https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
           sudo mv actionlint /usr/local/bin/
       - name: Lint GitHub Actions
         run: actionlint