doinstall v0.1.0

Source commit: cff2c74

Native Windows Server 2022 x64 and Ubuntu 22.04 x64 verification, archive inspection, and temporary-root install/package/uninstall acceptance passed.

Use the tools archive for CI or the setup executable for interactive installation. Check SHA256SUMS before running any downloaded file. Exact toolchains and per-platform file hashes are in RELEASE-METADATA.json. Linux baseline: Ubuntu 22.04 x64 / glibc 2.35; other platforms are not release-tested.