Terminal relay: answer Hammerhead's terminal sessions through the agent

When someone opens a terminal for this site, Hammerhead lists the session in the
site's config. The agent connects out to Hammerhead and joins that connection to
its own SSH server, so no port has to be open on an edge. The agent now reports
where its SSH server listens and that it can relay.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

go.mod

@@ -3,16 +3,16 @@ module git.veillax.com/Veillax/bamboo
 go 1.27.3
 
 require (
-	git.veillax.com/Veillax/reef v0.1.11
+	git.veillax.com/Veillax/reef v0.1.12
 	github.com/creack/pty v1.1.24
 	golang.org/x/crypto v0.58.0
+	golang.org/x/net v0.61.0
 	golang.org/x/time v0.7.0
 )
 
 require (
 	github.com/Microsoft/go-winio v0.6.4 // indirect
 	github.com/google/btree v1.1.2 // indirect
-	golang.org/x/net v0.61.0 // indirect
 	golang.org/x/sys v0.49.0 // indirect
 	golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 // indirect
 	golang.zx2c4.com/wireguard v0.0.0-20261024220952-b3bc704ef0ee // indirect