Extract the ssh debug commands into a transport neutral commands package (#1958)

Migrate commands from ssh into a transport neutral package

 - add golden tests validating that output remains unchanged
 - move commands to commands.go

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

go.mod

@@ -7,7 +7,6 @@ require (
 	filippo.io/bigmod v0.1.0
 	github.com/DefinedNet/netlink v1.3.2-dn.1
 	github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be
-	github.com/armon/go-radix v1.0.0
 	github.com/flynn/noise v1.1.0
 	github.com/gaissmai/bart v0.29.0
 	github.com/gogo/protobuf v1.3.2