docs: clarify think_deeper as second opinion tool

Updated descriptions to emphasize that:
- Gemini provides a "second opinion" to augment Claude's extended thinking
- Claude has its own extended thinking capabilities
- Gemini complements rather than replaces Claude's analysis
- Added "edge cases Claude might miss" to show collaborative value

This makes it clear that both AIs can do deep thinking, but together
they provide more comprehensive analysis through different perspectives.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: guidedways