refactor(demo): simplify visualizer wiring and typing

Apply Oracle-guided cleanup to make the demo pipeline contract explicit and remove defensive runtime indirection while preserving existing visualization behavior.

opengait/demo/visualizer.py

@@ -315,20 +315,30 @@ class OpenCVVisualizer:
         Returns:
             Displayable side-by-side image
         """
-        # Prepare individual views
-        raw_view = self._prepare_raw_view(mask_raw)
-        norm_view = self._prepare_normalized_view(silhouette)
-
-        # Convert to grayscale for side-by-side composition
-        if len(raw_view.shape) == 3:
-            raw_gray = cast(ImageArray, cv2.cvtColor(raw_view, cv2.COLOR_BGR2GRAY))
+        # Prepare individual views without mode indicators (will be drawn on combined)
+        # Raw view preparation (without indicator)
+        if mask_raw is None:
+            raw_gray = np.zeros((DISPLAY_HEIGHT, DISPLAY_WIDTH), dtype=np.uint8)
         else:
-            raw_gray = raw_view
+            if len(mask_raw.shape) == 3:
+                mask_gray = cast(ImageArray, cv2.cvtColor(mask_raw, cv2.COLOR_BGR2GRAY))
+            else:
+                mask_gray = mask_raw
+            raw_gray = cast(
+                ImageArray,
+                cv2.resize(
+                    mask_gray,
+                    (DISPLAY_WIDTH, DISPLAY_HEIGHT),
+                    interpolation=cv2.INTER_NEAREST,
+                ),
+            )
 
-        if len(norm_view.shape) == 3:
-            norm_gray = cast(ImageArray, cv2.cvtColor(norm_view, cv2.COLOR_BGR2GRAY))
+        # Normalized view preparation (without indicator)
+        if silhouette is None:
+            norm_gray = np.zeros((DISPLAY_HEIGHT, DISPLAY_WIDTH), dtype=np.uint8)
         else:
-            norm_gray = norm_view
+            upscaled = self._upscale_silhouette(silhouette)
+            norm_gray = upscaled
 
         # Stack horizontally
         combined = np.hstack([raw_gray, norm_gray])