ci: preserve executable mode for preview binaries

Author: kobzevvv

.github/workflows/mem-preview-release.yml

@@ -53,6 +53,7 @@ jobs:
           GH_TOKEN: ${{ github.token }}
         run: |
           set -euo pipefail
+          chmod 0755 dist/opencode-darwin-arm64 dist/opencode-linux-x64
           test "$(./dist/opencode-linux-x64 --version)" = '1.18.34'
           cd dist
           sha256sum opencode-darwin-arm64 opencode-linux-x64 > SHA256SUMS