dsh-uppercase: Uppercase Conversion Plugin

The DeepSeek Harness (DSH) plugin `dsh-uppercase` enforces uppercase formatting for text. Maintained by uckkk, it is implemented in pure Node.js with no network dependencies. Users can install it using the `dsh plugin add github:uckkk/dsh-uppercase` command. After installation, it can be used directly in a session by invoking the registered tool. It is suitable for scenarios that require consistent uppercase formatting. We recommend reviewing the source code before installation.