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>

.gitattributes

@@ -0,0 +1,2 @@
+# Goldens are compared byte for byte, so they must come out of git the way they went in.
+*.golden -text