dsh-web-search-nokey: Keyless Web Search Plugin for DeepSeek Harness

dsh-web-search-nokey is a no-key web search plugin for DeepSeek Harness (DSH), specifically designed to resolve the issue where `web_search` returns 401 errors when using credit-based configurations with Trae/WorkBuddy. It registers a WebSearchProvider that requires no credentials and forwards queries to public search interfaces. The plugin supports backends such as Bing RSS, web, and 360 Search, and offers environment variable and proxy configuration; it takes effect immediately after installation. However, note that 360 Search results are redirect shells, and unofficial APIs may be subject to rate-limiting risks.