feat: show live controller input

Route paired controller QoS data through the existing GIP protocol layer and
expose the latest gamepad report through the C API. Add a SwiftUI monitor for
buttons, d-pad, triggers, and stick positions without registering a native HID
device.

Co-Authored-By: openai/gpt-5.6-luna: GIP bridge and live input monitor

include/mt76/mt76.hpp

@@ -77,6 +77,12 @@ public:
     // then bulk-writes it to EP OUT.
     auto send_wlan(std::span<std::uint8_t const> frame) -> int;
 
+    // Send a GIP payload in an upstream QoS-data frame for one client.
+    auto send_client_frame(std::uint8_t wcid,
+                           std::span<std::uint8_t const> addr,
+                           std::span<std::uint8_t const> frame,
+                           bool encrypted) -> int;
+
     // Associate a controller: program its WCID MAC, ADD_CLIENT ms_command,
     // and transmit an ASSOC_RESP mgmt frame.
     auto associate_client(std::uint8_t wcid, std::span<std::uint8_t const> addr)