feat(installer): build worker source over SSH

docs/install.md

@@ -5,8 +5,12 @@ Docker image) into a running, enabled systemd service on a Linux host. It is
 the supported way to deploy the worker: it writes the configuration, the
 systemd unit, and the data directory, then starts the service.
 
-> A Go SSH source installer is planned in
-> [source-installation.md](source-installation.md). Today
+> A Go SSH source installer (`rsmon-worker source-install`) builds the worker
+> from source on a remote host over SSH - prerequisites, verified Go toolchain,
+> clone/update of the public repository (resolved to the remote default branch
+> unless pinned), resolved branch/commit record, and a staging build - without
+> yet installing a service. See
+> [source-installation.md](source-installation.md). Today the local
 > `install` copies the binary you invoke it from (or pulls the `--image`
 > digest), so build first with `make build` and run the resulting
 > `./bin/rsmon-worker`.