feat: complete wgcloak v1 transports

docs/PROTOCOL.md

@@ -44,8 +44,10 @@ timeout (target default 120 seconds), then its backend socket and replay state
 are released.
 
 The core rejects oversized application datagrams, increments a counter, and
-logs at debug/warn level. v1 does not fragment datagrams; a conservative
-starting limit is 1200 bytes.
+logs at debug/warn level. v1 does not fragment datagrams. The default
+application payload limit is 1200 bytes; configuration accepts values up to
+the project-wide 16,384-byte safety ceiling. The effective session maximum may
+be lower after transport framing and path negotiation.
 
 ## Encapsulated transports