dsh-qps-calc: Peak QPS Estimation

DeepSeek Harness (DSH) has released the community plugin `dsh-qps-calc`, designed to help developers quickly assess the peak concurrency of model inference services. Adhering to the “everything is a plugin” philosophy, the plugin allows precise QPS calculation by parameters directly within a session using the `qps_calc` tool. Implemented in pure Node.js with no network dependencies, the tool runs under the current process permissions and is suitable for rapid local evaluation. Installation requires the `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools` dependencies. Developers are advised to review the source code and license before installing.