fix: small fixes

internal/tunnel/frame.go

@@ -1,5 +1,5 @@
 // Package tunnel defines the framed multiplexing protocol used for DIRECT port
-// forwarding over the dedicated host port (default 8446). Unlike the HTTP
+// forwarding over the dedicated host port (DefaultPort). Unlike the HTTP
 // long-poll forward, this is a raw TCP stream the agent dials outbound; it
 // carries many concurrent forwarded connections (streams) for one agent and
 // has far lower latency than long-polling.