dsh-habits: Maintain user-global AGENTS.md in Web Settings

dsh-habits is a DeepSeek Harness (DSH) plugin designed to simplify the maintenance of the user's global instruction document `$DSH_HOME/AGENTS.md` through a web settings interface. The plugin provides a "My Habits" editor in the General area of DSH Web Settings, allowing users to directly edit and save preference or constraint text in their browser. Once saved, the text is automatically written to the AGENTS.md file and injected into subsequent sessions by DSH's built-in instructions loader. The plugin implements data read/write via REST interfaces `/api2/habits/describe` and `/api2/habits/update`, and adopts S...