add update_vocabulary dora input for runtime label changes

The open_vocab engine now accepts an update_vocabulary input event
carrying a UTF-8 comma-separated label string. Labels are re-encoded
immediately via the CLIP text encoder; the next tick uses the new
vocabulary. ZedNative ignores the input via a no-op base class method.

src/engines/engine.h

@@ -20,6 +20,7 @@ public:
 
     virtual void enable(sl::Camera& camera) = 0;
     virtual void detect(sl::Camera& camera) = 0;
+    virtual void set_labels(const std::string& /*labels*/) {}
     virtual const std::vector<DetectedObject>& objects() const = 0;
     virtual std::string label_names() const = 0;
 };

src/engines/open_vocab.cc

@@ -576,6 +576,11 @@ void OpenVocab::detect(const cv::Mat& image_bgr) {
     }
 }
 
+void OpenVocab::set_labels(const std::string& labels) {
+    config_.labels = labels;
+    encode_labels(labels);
+}
+
 const std::vector<DetectedObject>& OpenVocab::objects() const {
     return detected_;
 }

src/engines/open_vocab.h

@@ -30,7 +30,8 @@ public:
 
     void enable(sl::Camera& camera) override;
     void detect(sl::Camera& camera) override;
-    void detect(const cv::Mat& image_bgr);  // image-only; no 3D fusion
+    void detect(const cv::Mat& image_bgr);       // image-only; no 3D fusion
+    void set_labels(const std::string& labels) override;
     const std::vector<DetectedObject>& objects() const override;
     std::string label_names() const override;
 

src/main.cc

@@ -95,7 +95,18 @@ int main() {
         }
 
         auto input = event_as_input(std::move(event));
-        (void)input;
+        std::string input_id = std::string(input.id);
+
+        if (input_id == "update_vocabulary") {
+            if (!input.data.empty()) {
+                std::string labels(
+                    reinterpret_cast<const char*>(input.data.data()),
+                    input.data.size());
+                detector->set_labels(labels);
+                std::cout << "Vocabulary updated: " << labels << std::endl;
+            }
+            continue;
+        }
 
         if (!camera.grab()) {
             std::cerr << "Grab failed; attempting to reconnect..." << std::endl;