🧹 chore: address minor issues

[danny-avila]

Summary

• Added a submitting CSS selector to prevent blinking cursor for empty, non-latest, non-streaming messages, improving the visual consistency of the chat interface.
• Enhanced error handling in the OpenAIClient's chat completion process to manage scenarios where the response has no choices or the message is undefined.
• Adjusted the Markdown component to only show the thinking animation for the latest message.

Testing

To test these changes:

1. Start a new conversation and observe the cursor behavior for messages in different states (latest, non-latest, streaming, non-streaming).
2. Simulate error scenarios in the OpenAIClient to verify the improved error handling.
3. Check the console logs for the new debugging statements in various chat completion scenarios.

Test Configuration:

• Ensure you have the latest dependencies installed.
• Test with different AI models and conversation lengths to verify consistent behavior.

Checklist

• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• I have commented in any complex areas of my code
• My changes do not introduce new warnings
• I have tested the changes in various scenarios to ensure robustness