Add gpudemod DLL override path and document Windows warning

README.md

@@ -51,6 +51,8 @@ Important:
 - `build-sdrplay.ps1` prepares the runtime DLL placement and PATH setup for SDRplay + CUDA DLLs
 - the gpudemod DLL is built with `-cudart=hybrid`
 - GPU validation is disabled by default for performance; enable it with `SDR_GPU_VALIDATE=1` when debugging
+- you can override DLL lookup with `GPUMOD_DLL=C:\path\to\gpudemod_kernels.dll`
+- Windows builds may still show a harmless `__cdecl redefined` warning from CUDA headers
 - older experimental Windows build scripts were removed to avoid confusion
 
 ### Linux

internal/demod/gpudemod/gpudemod_windows.go

@@ -124,6 +124,9 @@ func ensureDLLLoaded() error {
 				filepath.Join(wd, "internal", "demod", "gpudemod", "build", "gpudemod_kernels.dll"),
 			)
 		}
+		if env := os.Getenv("GPUMOD_DLL"); env != "" {
+			candidates = append([]string{env}, candidates...)
+		}
 		seen := map[string]bool{}
 		for _, p := range candidates {
 			if p == "" || seen[p] {