dsh-model-search: Add search box for DSH Web model switching

dsh-model-search is a plugin designed for the DeepSeek Harness (DSH) Web interface, aiming to address the difficulty of locating models when the list is excessively long. This plugin adds a search box at the top of the model switching component, supporting filtering by model name, model ID, or Provider name. The matching process is case-insensitive and tokenized by spaces. Groups with no matches are automatically hidden, while preserving the official reasoning level selection, status indicators, and interaction logic. Users can enable the plugin by installing it via the `dsh plugin --profile web add dsh-model-search` command and restarting the service. The plugin achieves its functionality by replacing the official component; if an upstream DSH upgrade causes component changes, rebuilding and manually adapting patch anchors may be required. Additionally, the search box supports...