dsh-web-search-responses: DSH search provider reusing Responses' built-in web_search

`dsh-web-search-responses` is an MIT-licensed DSH plugin designed to address the search request forwarding issue when custom models use the OpenAI Responses endpoint with built-in `web_search`. This plugin registers a search provider named `responses-web`, enabling `ctx.web.search()` to reuse the Responses API endpoint of the current session's model to send built-in `web_search` requests and parse the response results. By default, it automatically follows the current model and route, but also supports explicitly fixed routes. Key configuration options include `provider`, `model`, `baseURL`, `apiKeyEnv`, and search parameters. Installation can be performed via GitHub or a local path.