Integrate Self-hosted Search and Crawling into DeepSeek Harness Using surfing-plugin

The `surfing-plugin` is maintained by cyijun, which connects the native `web_search` and `web_fetch` from DeepSeek Harness to self-hosted SearXNG and Crawl4AI. It registers `surfing-searxng` and `surfing-crawl4ai` to `ctx.web` without altering tool names, parameters, or result truncation. The directory page installation command is `dsh plugin add github:cyijun/surfing-plugin`, it is recommended to pin the commit hash, and first confirm that SearXNG has enabled JSON functionality and Crawl4AI is accessible. The plugin runs with the permissions of the current `dsh` process, and the source code and MIT license should be checked before installation.