feat: Side-by-side layout with chat and visualization

Changed from stacked to side-by-side layout for better UX:

Before (stacked):
- Chat messages on top
- Visualization below
- Had to scroll to see both

After (side-by-side):
- Chat on left (2/3 width)
- Visualization on right (1/3 width)
- See both simultaneously
- Fixed height of 600px for both

Layout structure:
┌─────────────────────────┬──────────────┐
│ Chat Messages │ Visualization│
│ (scale=2) │ (scale=1) │
│ │ │
│ Message Input │ │
└─────────────────────────┴──────────────┘

Benefits:
- Better use of screen space
- View segmentation/grounding while chatting
- More professional clinical interface
- Similar to PACS viewer layouts

Co-Authored-By: Claude <[email protected]>

app.py

@@ -271,19 +271,26 @@ with gr.Blocks() as demo:
             info="Assistant Mode: Direct answers | Tutor Mode: Socratic guidance through questions"
         )
 
-    # Use type="messages" for newer Gradio versions on HF Spaces
-    try:
-        chatbot = gr.Chatbot(type="messages")
-    except TypeError:
-        # Fallback for older Gradio versions
-        chatbot = gr.Chatbot()
-    viz_output = gr.Image(label="Visualization (Grounding/Segmentation)", visible=True)
-
-    msg = gr.MultimodalTextbox(
-        label="Message",
-        placeholder="Upload an X-ray image (JPG, PNG, DICOM) and ask a question...",
-        file_types=["image", ".dcm", ".dicom", ".DCM", ".DICOM"]
-    )
+    # Side-by-side layout: Chat on left, Visualization on right
+    with gr.Row():
+        # Left column: Chat interface
+        with gr.Column(scale=2):
+            # Use type="messages" for newer Gradio versions on HF Spaces
+            try:
+                chatbot = gr.Chatbot(type="messages", height=600)
+            except TypeError:
+                # Fallback for older Gradio versions
+                chatbot = gr.Chatbot(height=600)
+
+            msg = gr.MultimodalTextbox(
+                label="Message",
+                placeholder="Upload an X-ray image (JPG, PNG, DICOM) and ask a question...",
+                file_types=["image", ".dcm", ".dicom", ".DCM", ".DICOM"]
+            )
+
+        # Right column: Visualization
+        with gr.Column(scale=1):
+            viz_output = gr.Image(label="Visualization (Grounding/Segmentation)", height=600)
 
     def respond(message, chat_history, mode_selection):
         # Convert mode selection to internal mode string