dsh-sort-unique: Sorting and Deduplication Plugin

`dsh-sort-unique` is a pure Node.js DeepSeek Harness plugin developed by uckkk. It focuses on sorting and deduplicating input lists without requiring network access. Install it using `dsh plugin add github:uckkk/dsh-sort-unique`. When using it, ensure the environment meets the dependency requirements of `@deepseek-ai/cordis` ^4.0.1 and `@deepseek-ai/dsh-tools` >=0.1.0-rc.6. It is suitable for lightweight workflow scenarios that process list data locally.