Possible memory leak: model path C.CString is never freed in NewOnnx

# Possible memory leak: model path C.CString is never freed in NewOnnx

`NewOnnx` passes the model path to `CreateSession` as an inline `C.CString`. The
allocation is not bound to a variable, so there is no name available to free it
afterwards.

go/onnx/onnx_runtime.go:21

```go
if err := C.CreateSession(ort.api, C.CString(modelPath), &ort.session, &ort.memory); err != nil {
return nil, fmt.Errorf("create session: %v", C.GoString(C.GetErrorMessage(err)))
}
```

go/onnx/onnx_runtime.h:15

```c
OrtStatus *CreateSession(const OrtApi *ort, const char *model, OrtSession **session, OrtMemoryInfo **memory_info) {
...
RETURN_ON_ERROR(ort->CreateSession(env, model, options, session));
```

`model` is taken as `const char *` and handed to `OrtApi::CreateSession`, which
copies the path. Nothing takes ownership of the buffer, and `CreateSession` does
not free it, so the string leaks on every call, on both the success and the
error path.

Fix:

```go
cPath := C.CString(modelPath)
defer C.free(unsafe.Pointer(cPath))
if err := C.CreateSession(ort.api, cPath, &ort.session, &ort.memory); err != nil {
```

with `#include ` in the preamble.

Separately, `RETURN_ON_ERROR` in `CreateSession` returns before releasing `env`
and `options`, and the `OrtStatus` returned to Go is never passed to
`ReleaseStatus`.

If you could credit me as a reporter for my contributions to security advisory I will be thankful.

Start in go/onnx/onnx_runtime.go at NewOnnx and inspect the C.CreateSession call, then read onnx/onnx_runtime.h and its CreateSession cleanup paths. Confirm the model-path allocation and the separately noted environment, options, and status lifetimes on both success and error paths. Done means the reported allocations are released without changing session creation behavior.

Written by the indexing model from the issue text.