* ci: add test for Windows CMD wrapper
This test will fail until the CMD wrapper is fixed to call the native binary.
* fix: Windows CMD wrapper calls native binary instead of missing index.js
The download-artifact action creates directories named after each artifact.
When downloading to bin/, this caused conflicts because the artifact directory
names matched the binary names (e.g., bin/agent-browser-darwin-arm64/agent-browser-darwin-arm64).
Fix by downloading to artifacts/ first, then using find to move the binaries to bin/.