add open-vocab YOLO-World engine with CLIP text encoder

- Add OpenVocab engine: YOLO-World ONNX detection with runtime
  vocabulary via CLIP text embeddings (two-input model support)
- Add header-only C++ CLIP BPE tokenizer (no external deps)
- Add detect(cv::Mat) overload to OpenVocab for camera-free testing
- Add standalone test binary (test_open_vocab) using test/assets images
- Add export scripts for YOLO-World and CLIP text encoder (uv/PEP 723)
- Add installation scripts for Linux x64, ARM (Jetson), and Windows
- Update CMakeLists to use find_package(onnxruntime) instead of FetchContent
- Update README and AGENTS with env vars, setup workflow, and test usage

src/engines/engine.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <sl/Camera.hpp>
+#include <string>
+#include <vector>
+
+namespace engines {
+
+struct DetectedObject {
+    int label_id;
+    float confidence;
+    float position[3];         // center x, y, z (mm)
+    float bounding_box_2d[8];  // 4 corners × 2 coords (pixels)
+    float bounding_box_3d[24]; // 8 corners × 3 coords (mm)
+};
+
+class Engine {
+public:
+    virtual ~Engine() = default;
+
+    virtual void enable(sl::Camera& camera) = 0;
+    virtual void detect(sl::Camera& camera) = 0;
+    virtual const std::vector<DetectedObject>& objects() const = 0;
+    virtual std::string label_names() const = 0;
+};
+
+} // namespace engines