Speak protocol 3.0 and fall back to 2.0 only when that is the reflector's maximum.

A reflector that has moved to 3.0 will not accept a station that always announces 2.0, and a 2.x reflector still needs one explicit plaintext session.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/dist/app.js

@@ -21,6 +21,8 @@ function render(state) {
   document.getElementById("connection").textContent = state.connection;
   document.getElementById("callsign").textContent = state.callsign;
   document.getElementById("talkgroup").textContent = String(state.talkGroup);
+  const protocol = document.getElementById("protocol");
+  protocol.textContent = state.protocol ? "Protocol " + state.protocol : "";
   document.getElementById("detail").textContent = line(state);
   button.classList.toggle("down", !!state.transmitting);
 }