test(installer): add OpenSSH distro harness

README.md

@@ -177,6 +177,12 @@ SSH host keys are checked against `~/.ssh/known_hosts` by default. Use
 `--insecure-host-key` option disables host authentication and should only be
 used in a trusted disposable environment.
 
+A Go SSH source installer (remote package/toolchain/source build) is planned;
+the pure detection/planning layer and the Docker/OpenSSH test harness that will
+accept it are implemented. See
+[`docs/source-installation.md`](docs/source-installation.md); run the live
+fixture matrix with `make test-ssh`.
+
 ## Configuration
 
 | Variable | Required | Default | Purpose |