Add AgentGuard to Tools section

[bmdhodl]

Added AgentGuard to the Tools section.

AgentGuard is a zero-dependency Python SDK for AI agent observability and runtime guardrails:

• Loop detection: Catches repeated tool calls in a sliding window
• Budget enforcement: Hard dollar/token/call limits
• Cost tracking: Per-call dollar estimates (OpenAI, Anthropic, Gemini, Mistral)
• Trace visualization: Gantt timeline viewer
• Deterministic replay: Record and replay for regression testing
• LangChain integration: Native BaseCallbackHandler

Install: pip install agentguard47
License: MIT
PyPI: https://pypi.org/project/agentguard47/