dsh-better-retry: Retry All Failed Model Requests

`dsh-better-retry` is a DeepSeek Harness plugin designed to resolve the limitation of the default retry plugin, which only handles whitelisted errors. It does not rely on a whitelist, retries all errors, supports an exponential backoff strategy, and provides a UI slider for real-time configuration of the retry count (0–64) and 429 wait duration (5–120s). The plugin automatically excludes `ABORTED` and `CONTEXT_WINDOW_EXCEEDED` errors to ensure session safety. After installation, the configuration is persisted, making it suitable for unstable scenarios such as API rate limiting and significantly improving request success rates.