feat: implement local decision engine for offline operation

## Description
NanoClaw must operate autonomously when disconnected from MoltClaw (L3). Implement a simple rule-based decision engine.

## Requirements
- [ ] Rule definition format (YAML/JSON)
- [ ] Threshold-based alerting (e.g., temp > 35C -> alert)
- [ ] Local action execution (GPIO, relay, notification)
- [ ] Decision log for later sync to L3

## Skills
Python, rule engines