prompt: simplify child-friendly responses

[aazeeem11]

What changed

• Simplified base and child-friendly prompts to improve clarity for kids (ages 5–12).

Why

• Improves response consistency and readability (Issue Improve RAG Agent response. #20).

Scope

• Prompt-only change. No logic or parameter changes.

Testing

• Tested locally via /ask endpoint.

[chimosky]

The prompt looks encouraging, I can't test right now and seeing as you've tested, it'll be great to share the responses before and after your test, then it'll be easier to tell if it's better. Thank you!