dsh-web-search-anysearch: AnySearch Web Search Plugin

`dsh-web-search-anysearch` is the AnySearch web search plugin for DeepSeek Harness, providing out-of-the-box internet access. The plugin uses a stateless design, supports fixed domains and anonymous access, utilizes the unified `ctx.web` interface to handle search results, and parses Markdown into citable sources. Installation requires DSH >= 0.2.0-rc.2 and supports configuring an API key, search parameters, and timeouts. The plugin is mounted to the `web_search` engine by default and supports up to 10 results.