dsh-done-whale: Turn the DeepSeek Harness tab whale into a status light

`dsh-done-whale` is a browser tab status indicator plugin for the official DeepSeek Harness (DSH), designed to address the difficulty in distinguishing icons when running multiple sessions in parallel. Leveraging the official plugin mechanism without requiring additional dependencies, this plugin dynamically converts the whale icon on the tab into color status indicators: green indicates that a session has completed while the user was not viewing it, amber indicates a session waiting for user action (such as a question, approval, or review), and black is the default status. When both states are present simultaneously, green takes priority; the plugin responds only to the main session, and sub-agent sessions do not trigger color changes. Users can install it simply by executing `dsh plugin --profile web add dsh-done-whale` via the command line, and the changes will take effect after restarting or refreshing the page. Clicking on the corresponding session automatically restores the status.