Load WinML runtime DLL for SDK EP discovery (#733)

## Summary
- Load `Microsoft.Windows.AI.MachineLearning.dll` from the Core native
directory for the Python SDK when present.
- Preload the same WinML runtime DLL for Rust `winml` builds from the
native runtime directory.
- Preload the WinML runtime DLL for C# WinML builds alongside ORT and
ORT GenAI.
- No JS SDK code change needed; its existing loader already handles the
native runtime directory.

## Validation
- Rust WinML EP smoke without a caller PATH override discovered CUDA,
OpenVINO, and NvTensorRTRTX, then registered OpenVINO.
- C# WinML source smoke without a caller PATH override discovered CUDA,
OpenVINO, and NvTensorRTRTX, then registered OpenVINO.
- JS EP smoke without a caller PATH override discovered CUDA, OpenVINO,
and NvTensorRTRTX, then registered OpenVINO.

---------

Co-authored-by: Prathik Rao <prathikrao@microsoft.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Bhagirath Mehta <bhamehta@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 5 people

sdk/python/src/detail/core_interop.py

@@ -132,6 +132,7 @@ class CoreInterop:
     _flcore_library = None
     _genai_library = None
     _ort_library = None
+    _winml_library = None
 
     instance = None
 
@@ -182,6 +183,17 @@ def _initialize_native_libraries() -> 'NativeBinaryPaths':
         if sys.platform.startswith("win"):
             CoreInterop._ort_library = ctypes.CDLL(str(paths.ort))
             CoreInterop._genai_library = ctypes.CDLL(str(paths.genai))
+            winml_path = paths.core_dir / "Microsoft.Windows.AI.MachineLearning.dll"
+            if winml_path.exists():
+                # only exists in the WinML variant, load if present so that Core can use WinML EPs
+                try:
+                    CoreInterop._winml_library = ctypes.CDLL(str(winml_path))
+                except OSError as e:
+                    logger.warning(
+                        "Failed to load optional WinML library '%s'; continuing without WinML EPs: %s",
+                        winml_path,
+                        e,
+                    )
         else:
             CoreInterop._ort_library = ctypes.CDLL(str(paths.ort), mode=os.RTLD_GLOBAL)
             CoreInterop._genai_library = ctypes.CDLL(str(paths.genai), mode=os.RTLD_GLOBAL)

sdk/rust/src/detail/core_interop.rs

@@ -787,6 +787,25 @@ impl CoreInterop {
             }
         }
 
+        #[cfg(feature = "winml")]
+        {
+            let winml_dep = "Microsoft.Windows.AI.MachineLearning.dll";
+            let winml_path = dir.join(winml_dep);
+            if winml_path.exists() {
+                // The WinML feature uses the WinML Core package and copies this
+                // DLL into the native directory; load it from there so callers
+                // don't need to add that directory to PATH.
+                // SAFETY: Pre-loading a known dependency DLL from the same trusted
+                // directory as the core library.
+                let lib = unsafe {
+                    Library::new(&winml_path).map_err(|e| FoundryLocalError::LibraryLoad {
+                        reason: format!("Failed to load dependency {winml_dep}: {e}"),
+                    })?
+                };
+                libs.push(lib);
+            }
+        }
+
         Ok(libs)
     }
 }