feat: pair controllers and show them in the app

Port the MT76 client functions (send_wlan, associate_client,
pair_client, set_client_key, remove_client) and wire the RX dispatch
into the session: EP IN frames are parsed, ASSOC_REQ associates a
controller (WCID plus chip programming), PAIR_REQ replies with
PAIR_RESP, and DISASSOC or client-lost removes it. The C API exposes
connected controllers and the app lists them by MAC. Bumps
xone_cli/xone_app to C++23: they were falling back to the default
standard once mt76.hpp started using std::span. Adds a unit test pinning
the WCID regions, the 32-byte rxwi, and the new frame control values.

Co-Authored-By: qwen3.8-27b@q2_k_xl: client functions, RX dispatch, GUI list

src/app/main.swift

@@ -30,6 +30,8 @@ struct ContentView: View {
     // Radio state polled from the background worker each tick; a change here
     // is what re-renders the debug section.
     @State private var radioState = XONE_STATE_IDLE
+    // Connected controllers (MAC strings), refreshed each tick.
+    @State private var controllers: [String] = []
 
     private let timer = Timer.publish(every: 1.0, on: .main, in: .common)
         .autoconnect()
@@ -84,6 +86,7 @@ struct ContentView: View {
                 session = nil
             } else if let s = session {
                 radioState = Int(xone_state(s))
+                refreshControllers(s)
             }
             donglePresent = present
         }
@@ -130,6 +133,19 @@ struct ContentView: View {
         return build.isEmpty ? "not loaded" : build
     }
 
+    // Query the C API for connected controllers and store their MACs.
+    private func refreshControllers(_ session: OpaquePointer) {
+        let count = Int(xone_controller_count(session))
+        var list: [String] = []
+        for i in 0..<count {
+            var buf = [CChar](repeating: 0, count: 18)
+            if xone_controller_mac(session, Int32(i), &buf, 18) == 0 {
+                list.append(String(cString: buf))
+            }
+        }
+        controllers = list
+    }
+
     private var statusView: some View {
         HStack(spacing: 8) {
             Circle()
@@ -144,8 +160,19 @@ struct ContentView: View {
         VStack(alignment: .leading, spacing: 8) {
             Text("Controllers")
                 .font(.headline)
-            Text("No controllers connected.")
-                .foregroundStyle(.secondary)
+            if controllers.isEmpty {
+                Text("No controllers connected.")
+                    .foregroundStyle(.secondary)
+            } else {
+                ForEach(controllers, id: \.self) { mac in
+                    HStack {
+                        Image(systemName: "gamecontroller")
+                            .foregroundStyle(.secondary)
+                        Text(mac)
+                            .font(.system(.body, design: .monospaced))
+                    }
+                }
+            }
         }
     }
 }