dsh-rot: Letter Shift Plugin

The DSH plugin dsh-rot, maintained by uckkk, provides letter displacement functionality. It is implemented purely in Node.js, requires no network requests, and is lightweight and efficient. It can be installed with the command `dsh plugin add github:uckkk/dsh-rot` and used by calling it directly in a session. Before use, ensure that the environment meets the dependencies `@deepseek-ai/cordis` (^4.0.1) and `@deepseek-ai/dsh-tools` (>=0.1.0-rc.6), and review the source code and license.