dsh-model-search: Adding Searchable Filtering to the DeepSeek Harness Model Selector

`dsh-model-search` is a DeepSeek Harness plugin maintained by a1073097082, designed to solve the cumbersome problem of finding models in the model selector. This plugin adds a searchable filtering feature to the model selector, allowing users to quickly locate candidate models by vendor name, model name, or model ID. Its core features include support for case-insensitive keyword search, as well as allowing spaces to act as wildcards (for example, entering "GPT 6" can match both "GPT-5.6" and "GPT-6"). The plugin adopts a client-only overlay mechanism, does not alter model routing or credentials, and follows the MIT license. Users can install it by executing `dsh plugin --profile web add git`