Add native steering-wheel vertex substitution to Aurora

The VR first-person camera will animate the local vehicle's steering wheel
by handing Aurora a rotated copy of one of the vehicle's position arrays.
A draw picks up the copy only when it binds that exact array with the local
vehicle's position matrix (per-position ownership for indexed-matrix
draws), so opponents sharing the asset keep the original vertices. The copy
takes the same padded upload path as the original and never touches the
shared array cache.

Ported from heurazy's mario-kart-wii-VR-port (GPL-3.0-or-later).

aurora-main/include/aurora/aurora.h

@@ -251,6 +251,20 @@ void aurora_set_stereo_scene_anchor(const float anchorFromScene[12]);
 // Producer-thread, per-frame metadata, consumed by the next end_frame call.
 // One (the default) keeps full-frame replay. Desktop rendering is unaffected.
 void aurora_set_stereo_local_player_count(uint32_t count);
+/**
+ * VR native steering wheel: replacement position arrays for the local vehicle.
+ *
+ * GX (command processor) thread only, in order with the frame's draws: a host
+ * that runs GX on its own thread must post these there. `source` is the host
+ * pointer the game binds with GXSetArray; `replacement` is copied (at most 64
+ * KiB) and applies solely to draws that bind that array with a position matrix
+ * equal to `modelView` (row-major 3x4), so shared opponent models stay intact.
+ * Clearing reports how many draws the previous set matched.
+ */
+void aurora_clear_native_wheel_vertices(void);
+void aurora_set_native_wheel_vertices(const void* source, const void* replacement, uint32_t size,
+                                      const float* modelView);
+uint32_t aurora_native_wheel_draw_count(void);
 typedef void (*AuroraFrameWorkerWaitCallback)();
 // Called from the producer thread at bounded intervals while Aurora waits for
 // the asynchronous frame worker. The callback must not enter Aurora.