Cross-platform detect-before-install discipline for language runtimes, package managers, and build tools. Works on macOS, Linux (Debian/RHEL/Arch/Alpine), Windows (PowerShell + WSL), and inside CI/container environments. Loads platform-specific recipes on demand from platforms/{macos,linux,windows}.md and short-circuits installs when running under CI/container per ci-and-containers.md. Use BEFORE any install command in build-test-agent, code-generator, and workspace-scout.
