dshbase-catalog: Querying the Plugin Catalog in DeepSeek Harness

The dshbase-catalog plugin addresses the need to query the community plugin directory directly within DSH sessions. It maintains a daily updated index and supports full-text search, category listings, plugin detail queries, and statistics retrieval under the permissions of the current process. Once installed, it enables quick access to plugin installation commands and validation status through multiple tools (such as search_dsh_plugins, get_dsh_plugin, etc.).