falser101/dsh-mascot: Add a draggable floating mascot to DSH Web

`falser101/dsh-mascot` is an MIT-licensed plugin for DeepSeek Harness (DSH) Web, designed to address the unintuitive nature of session states during long tasks. The plugin maps the current session stage in real-time through a draggable cartoon mascot (cat or dog), such as states like queuing, thinking, calling tools, writing answers, and errors, accompanied by dynamic text and expression changes. As a pure frontend projection, it does not send events to the session but only provides visual cues. Core features include support for mouse dragging, automatic collapse on idle, and window adaptation; status bubbles with customizable text frequency and the option to enable tool name display; and parallel task notifications that display the number of busy sessions in the top-right corner with support for clicking to jump. It also features an "AI Theater" function (disabled by default) that can invoke the model to generate witty remarks. The plugin supports switching between Chinese and English text and respects system settings.