dsh-camel: DeepSeek Harness Free Model Rate Limit Recovery and Adaptive Throttling Plugin

`dsh-camel` is an optional plugin for DeepSeek Harness designed to address the issue of free models frequently triggering rate limits. It provides provider- and model-based adaptive quota learning, proactive request throttling, and a retry mechanism that respects `Retry-After` headers. After installation, throttling, retry, and adaptive throttling features must be enabled through configuration or command-line options. The plugin focuses solely on rate-limit boundary handling and does not invoke any LLM, effectively improving the success rate of requests to free models.