feat: simplify ask_followup_question prompt documentation

- Reduce documentation from ~45 lines to ~17 lines (~60% reduction)
- Simplify description and parameter explanations
- Consolidate from 2 examples to 1 concise example
- Keep old XML attribute format for backward compatibility
- Update all related snapshot tests

This helps prevent excessive questioning behavior with newer models while
maintaining the same functionality with the existing XML format.

Author: daniel-lxs