dsh-llm-net-retry: Bounded Retry Plugin for Network Failures in DeepSeek Harness

`dsh-llm-net-retry` is a non-intrusive plugin for DeepSeek Harness (dsh) designed to address the issue where the native policy misclassifies transient network failures (such as `network_error` and `unexpected EOF`) as non-retryable. It provides a bounded retry mechanism that intervenes only when the native policy abstains and the error falls into a blind spot. It supports configurable retry counts and backoff strategies, is stateless and leaves no residue, and is compatible with dsh >= 0.1.7-rc.1.