Add CI that runs tests, typecheck, and build verification on push/PR to master. Include test script in package.json and new .github/workflows/ci.yml. Adds: - .github/workflows/ci.yml: CI workflow with test, typecheck, and build jobs - package.json: test script entry 🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)