Update placeholder text for AI prompt
Context
The MVP version of AI integration was developed in #714 (closed).
Proposal
The current placeholder text is confusing because it's a specific prompt.
Replace the example prompt with more meaningful placeholder text:
How can I help you? Type your prompt here.
Design
[Include sketch or wireframes of the UI changes necessary for this feature]
Implementation (if applicable)
[A description of the steps to implement the feature.]
Alternative approaches (if applicable)
[Include any alternatives to meet this use case.]
Open issues (if applicable)
[Links to and a discussion of related issues, if applicable.]