Initial snapshot: hand motion pipeline (Dyn-HaMR + dex-retargeting + SPIDER)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

third_party/vipe/csrc/utils_ext/utils_bind.cpp

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+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <torch/extension.h>
+
+std::vector<torch::Tensor> nearestNeighbours(torch::Tensor query, torch::Tensor tree, int knn);
+
+void pybind_utils_ext(py::module &m) {
+    m.def("nearest_neighbours", &nearestNeighbours, "KNN computation (CUDA) distance is squared L2.", py::arg("query"),
+          py::arg("tree"), py::arg("knn"));
+}