Add Mem0, Zep, and LangGraph memory baselines

[CaspianG]

Goal: make the memory benchmark compare WaveMind with agent-memory systems, not only vector stores.

Targets:

• Mem0 baseline
• Zep baseline
• LangGraph persistent memory baseline

Expected output:

• adapters under benchmarks/ or wavemind/integrations/ where appropriate;
• one reproducible benchmark command;
• JSON result artifact under benchmarks/;
• README summary with precision/recall/latency and a short interpretation.

Important: this should stay honest. If a dependency needs an API key, cloud service, or paid setup, document that clearly and keep the offline path runnable.