dsh-model-gate: DSH Single-Model Disabling Gate

`dsh-model-gate` is a non-destructive plugin maintained by OPaimon that blocks specific models or provider routes in DSH without modifying the underlying configuration. It removes disabled models by intercepting the discovery path and returns a `MODEL_DISABLED` error during scheduling to block network requests. Users can install it via CLI and hot-apply settings in the Web settings panel. The configuration file supports exact matches and `*/model` wildcards. The plugin does not affect provider credentials, and leftover configuration after uninstallation is harmless.