The ssh install and ssh to commands (closes #2)

keyfunc ssh install appends the public line on a host through the system ssh, only when absent, feeding the line on standard input; keyfunc ssh to serves the derived key from an in-process agent on a private socket and runs the system ssh with it, the private key never on disk. Two review rounds; the second passed with no findings.

Model: opus-5 (implementation and review); fable-5-1 (landing)

internal/cli/ssh/ssh.go

@@ -17,7 +17,7 @@ func Command() *cobra.Command {
 		Short: "derive ed25519 SSH keys",
 	}
 
-	group.AddCommand(public(), private())
+	group.AddCommand(public(), private(), install(), to())
 
 	return group
 }