feat: replace capsule counting with screw_bag (2 screws + 3 nuts individually detected)

app.py

@@ -243,12 +243,12 @@ EXAMPLES = [
         "The first image is a normal sample. Please locate the defects within the second image with bounding box in JSON format.",
         256,
     ],
-    # 6. Object Counting (single image) — capsules
+    # 6. Object Counting + Detection (single image) — screw bag
     [
         None,
-        "examples/capsules_count.jpg",
-        "Count the number of capsules in this image. Give the exact number.",
-        128,
+        "examples/screw_bag_count.jpg",
+        "How many screws and nuts are in this image? For each one, give its bounding box as {\"bbox_2d\": [x1,y1,x2,y2], \"label\": \"type_N\"}.",
+        512,
     ],
     # 7. Industrial OCR (single image) — drink bottle
     [