API Usage Optimization

Update AGENTS.md: Added a new "Memory Hygiene" section to ALMA's agent prompt with four rules:

• Token budget grows with memory files. Periodically review and compress.
• Move important lessons from daily files into MEMORY.md
• Remove outdated entries from MEMORY.md
• Mental notes don't survive sessions. If it matters, write it to a file.

Breave Serach API: Enabled Brave Search API in openclaw.

This optimizations were necessary due to increasing API costs.