dsh-geoserver: DeepSeek Harness GeoServer Interactive Plugin

The `dsh-geoserver` plugin on the DSH platform provides GeoServer interaction capabilities for GIS scenario agents, replacing cumbersome manual API operations. It offers four types of tools—resource enumeration, data publishing (GeoTIFF/ZIP), map retrieval (WMS), and connectivity diagnostics—and supports visual configuration. The plugin manages credentials on the plugin side, provides a same-origin image service, and includes configuration notes for publishing restrictions and image caching. Agents can use CLI tools to perform complete GeoServer management directly within the session flow.