dsh-loop-guard: Result-Aware Loop Detector

The `dsh-loop-guard` plugin addresses the problem of agents in DeepSeek Harness getting stuck in infinite loops of repeated calls through a result-aware mechanism. It tracks identical tool names, arguments, and results, and enforces blocking using soft and hard thresholds: the soft phase issues prompts, while the hard phase rejects calls. The plugin supports legitimate polling and re-reading, and allows users to intervene and reset state, thereby effectively improving resource utilization efficiency.