Initial commit: win32 vGPU stream capture module

Capture backends (NvFBC/DDA/GDI), cursor/region/present helpers, publish API, vendor NvFBC headers; CMake build with mingw-w64 toolchain.

src/stream/win32/cursor.h

@@ -0,0 +1,16 @@
+#ifndef VGPU_CURSOR_H
+#define VGPU_CURSOR_H
+
+/* cursor.h — win32 GDI cursor sample/compose onto a tight BGRA frame. */
+
+#include <stdint.h>
+#include "ctx.h"           /* win32 vgpu_ctx (cursor state) */
+
+/* Sample the current cursor (position/shape) into ctx->cursor.
+ * Returns 1 if anything changed since last sample, else 0. */
+int  cursor_sample(vgpu_ctx* ctx);
+
+/* Alpha/AND-XOR compose the sampled cursor onto a tight BGRA frame. */
+void cursor_draw(vgpu_ctx* ctx, uint8_t* bgra, uint32_t width, uint32_t height);
+
+#endif /* VGPU_CURSOR_H */