WIP: checkpoint Wii native IMU and upstream IR bridge

Pause Wii pointing work with firmware 0.33-wii-trace installed. Preserve the pinned libogc IR pipeline, calibrated native IMU, software BOOTSEL, and standard camera sensitivity trial.

Tracking instability, tracking loss, and ineffective vertical movement remain unresolved. Level-2 camera filtering is not hardware-qualified. Nine targeted regression tests pass; firmware and persistent storage were verified after flashing.

tools/switch2_usb_probe/bootsel.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "tusb.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Core 0: expose only the existing private BOOTSEL command, not configuration.
+bool probe_bootsel_vendor_control(uint8_t rhport, uint8_t stage,
+                                  const tusb_control_request_t* request);
+// Core 0: service the existing reboot delay only after a validated status ACK.
+void probe_bootsel_task(uint32_t now_ms);
+
+#ifdef __cplusplus
+}
+#endif