dsh-agent-preset-router: Automatic Mode Routing Plugin for DeepSeek Harness

The `dsh-agent-preset-router` plugin provides an “automatic mode” for the DeepSeek Harness (DSH) Web Profile, addressing the hassle of manually switching between multiple presets. It uses a Flash model to anticipate user requests and automatically routes them to the most appropriate preset for execution, without requiring further confirmation. It supports displaying a decision info bar in the input box, and if classification fails, it automatically falls back to the default preset. Installation is simple and ready to use out of the box. Note that routing only applies to the first message of a conversation and cannot be canceled or retried midway. The plugin is open source and flexible, making it well suited for automated routing needs.