Harden UE Wingman request handling and numeric property conversion.

Switch the Wingman protocol to null-delimited JSON, rework the server's
socket buffering and send logic, and document the bugs found during the
review. Also refactor WingProperty's numeric setters into clearer helper
paths while preserving the existing conversion rules.

Plugins/UEWingman/ue-wingman.py

@@ -41,7 +41,7 @@ def main():
         print(f"Cannot connect to {HOST}:{PORT} — is the editor running?")
         sys.exit(1)
 
-    sock.sendall((json.dumps(msg) + "\n").encode())
+    sock.sendall((json.dumps(msg) + "\0").encode())
 
     result = b""
     while True: