Update custom visualizer documentation for new API

- Fix parameter name from 'visualize' to 'visualizer' throughout documentation
- Update visualization options to reflect simplified API:
  * Default behavior (no parameter): Creates default visualizer automatically
  * None: Disable visualization entirely
  * ConversationVisualizer instance: Use custom visualizer
- Improve error handling example with more practical code
- Align all examples with the API simplification changes

Related to: OpenHands/software-agent-sdk#1025

Co-authored-by: openhands <[email protected]>

Author: openhands-agent

sdk/guides/convo-custom-visualizer.mdx

@@ -17,7 +17,7 @@ The comprehensive example below demonstrates a custom visualizer that tracks con
 This example demonstrates how to create and use a custom visualizer by subclassing
 ConversationVisualizer. This approach provides:
 - Clean, testable code with class-based state management
-- Direct configuration (just pass the visualizer instance to visualize parameter)
+- Direct configuration (just pass the visualizer instance to visualizer parameter)
 - Reusable visualizer that can be shared across conversations
 - Better separation of concerns compared to callback functions
 
@@ -28,7 +28,7 @@ The MinimalProgressVisualizer produces concise output showing:
 - Error messages
 
 This demonstrates how you can pass a ConversationVisualizer instance directly 
-to the visualize parameter for clean, reusable visualization logic.
+to the visualizer parameter for clean, reusable visualization logic.
 """
 
 import logging
@@ -212,7 +212,7 @@ def main():
     conversation = Conversation(
         agent=agent,
         workspace=cwd,
-        visualize=minimal_visualizer,
+        visualizer=minimal_visualizer,
     )
 
     # Send a message and let the agent run
@@ -328,10 +328,10 @@ class CustomVisualizer:
             self.console.print(panel)
 
 # Use it directly
-conversation = LocalConversation(
+conversation = Conversation(
     agent=agent,
     workspace=workspace,
-    visualize=CustomVisualizer()  # Pass your custom object
+    visualizer=CustomVisualizer()  # Pass your custom object
 )
 ```
 
@@ -576,25 +576,33 @@ This pattern provides:
 Always include error handling to prevent visualization issues from breaking conversations:
 
 ```python
+import logging
+
 def on_event(self, event):
     try:
         # Your visualization logic
-        self._handle_event(event)
+        if isinstance(event, ActionEvent):
+            self._handle_action_event(event)
+        elif isinstance(event, ObservationEvent):
+            self._handle_observation_event(event)
+        # ... other event types
     except Exception as e:
         # Fallback to prevent breaking the conversation
-        print(f"Visualization error: {e}")
+        print(f"⚠️ Visualization error: {e}", flush=True)
         # Optionally log for debugging
-        logging.warning(f"Visualizer failed: {e}")
+        logging.warning(f"Visualizer failed for {event.__class__.__name__}: {e}")
 ```
 
+This pattern ensures that visualization problems never interrupt the agent's work.
+
 ### 5. Performance Considerations
 For high-frequency events, consider optimizing your visualization by filtering events or using efficient output methods like `flush=True` for immediate display.
 
 ## Using Your Custom Visualizer
 
 ### Direct Assignment (Recommended)
 
-Pass your visualizer instance directly to the `visualize` parameter:
+Pass your visualizer instance directly to the `visualizer` parameter:
 
 ```python
 # Create your custom visualizer
@@ -604,16 +612,16 @@ custom_visualizer = MinimalProgressVisualizer()
 conversation = Conversation(
     agent=agent,
     workspace="./workspace",
-    visualize=custom_visualizer,  # Direct assignment
+    visualizer=custom_visualizer,  # Direct assignment
 )
 ```
 
 ### Visualization Options
 
-The `visualize` parameter accepts three types:
+The `visualizer` parameter accepts three types:
 
-- **`True`** (default): Use the default Rich panel visualizer
-- **`False` or `None`**: Disable visualization entirely  
+- **Default behavior** (no parameter): Creates a default Rich panel visualizer automatically
+- **`None`**: Disable visualization entirely  
 - **`ConversationVisualizer` instance**: Use your custom visualizer
 
 ### Combining with Additional Callbacks
@@ -629,7 +637,7 @@ def metrics_callback(event):
 conversation = Conversation(
     agent=agent,
     workspace="./workspace", 
-    visualize=custom_visualizer,      # Handle visualization
+    visualizer=custom_visualizer,      # Handle visualization
     callbacks=[metrics_callback],     # Handle other concerns
 )
 ```