dsh-session-console: Add a central console to the DSH sidebar

A client-side plugin maintained by onlyinliu that expands the DSH sidebar conversation list into a dashboard covering all sessions: displaying global status, cumulative tokens and cache hit rate, cache hits, daily and weekly activity, context pressure, models, and a composite heat score, with support for filtering and sorting. It supports locating sessions using natural language (performing a weighted comparison against title, cwd, end of directory, preset, and session ID after stripping colloquialisms) and dispatching a sentence to a target session via queue or steer mode, retrieving the latest messages and failure reasons. Installation is performed via `plugin_manager install_bundle`, accepting either an npm package name or `github:onlyinliu/dsh-session-console`. After installation, DSH must be restarted for the icon to appear. For version 0.1.1, engines.dsh is set to `>=0.2.0-rc.2 <0.3.0-0`, fixing the `incompatible-version` issue caused by an overly narrow upper bound in 0.1.0.