dsh-session-steward: Session Steward

The DSH plugin `dsh-session-steward` is used to manage session history files and their health status. Its core features are divided into “Retirement Home” (browsing archives, unarchiving, and cleaning up files) and “Health Check-up” (four-gate diagnostics, batch scanning, and reversible repair). After installation, the DSH process must be restarted, and a new entry is added to the sidebar. The plugin provides two switches to control feature enablement. Note that a restart is required after operations, and write indexing is supported only in read-only mode.