DeepSeek Harness Plugin: dsh-web-search-session-follow

`dsh-web-search-session-follow` is a DeepSeek Harness plugin designed to address authentication failures of the built-in web search when users configure a proxy or use third-party gateways. It reads current session routing information to perform searches with the corresponding endpoint, credentials, and protocol dialect, and supports falling back to the official solution. The plugin supports three protocols—Anthropic, OpenRouter, and Zai—and provides visual priority configuration, connectivity testing, and audit logging, enabling flexible setup and resolving search availability issues in multi-gateway environments.