Fix duplicate parameter declaration in the face detector node

recognition_model was declared twice (once for the existence check, once for the
recognizer), so the node raised ParameterAlreadyDeclared at start-up and never
published. Declare each parameter once, and add a test that constructs the node,
since nothing else exercised it.

Recognition then works live: with the owner enrolled, 29 of 31 detections over
14 s were named, at detector scores around 0.9.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs

ros/hermes_vision/hermes_vision/face_detector_node.py

@@ -31,11 +31,13 @@ class FaceDetectorNode(Node):
         self.debug = bool(param('publish_debug', False))
         self.detector = FaceDetector(param('model_path', ''), float(param('score_threshold', 0.6)),
                                      int(param('min_size', 40)))
+        recognition_model = os.path.expanduser(param('recognition_model', DEFAULT_MODEL))   # declare once
+        faces_db = param('faces_db', DEFAULT_DB)
+        threshold = float(param('recognition_threshold', COSINE_THRESHOLD))
         self.recognizer = None
         if bool(param('recognize', True)) and self.detector.backend == 'yunet' \
-                and os.path.exists(os.path.expanduser(param('recognition_model', DEFAULT_MODEL))):
-            self.recognizer = FaceRecognizer(param('recognition_model', DEFAULT_MODEL), param('faces_db', DEFAULT_DB),
-                                             float(param('recognition_threshold', COSINE_THRESHOLD)))
+                and os.path.exists(recognition_model):
+            self.recognizer = FaceRecognizer(recognition_model, faces_db, threshold)
         self.pub = self.create_publisher(Detection2DArray, '/vision/faces', 10)
         self.debug_pub = (self.create_publisher(CompressedImage, '/vision/faces/debug/compressed', 1)
                           if self.debug else None)

ros/hermes_vision/test/test_node.py

@@ -0,0 +1,15 @@
+import pytest
+
+rclpy = pytest.importorskip('rclpy')
+
+
+def test_the_node_constructs_with_default_parameters():
+    """Declaring a parameter twice raises at construction, and nothing else exercises the node."""
+    from hermes_vision.face_detector_node import FaceDetectorNode
+    rclpy.init()
+    try:
+        node = FaceDetectorNode()
+        assert node.detector.backend in ('yunet', 'haar')
+        node.destroy_node()
+    finally:
+        rclpy.shutdown()