dsh-learning-plugin: An Example Tool for Learning the Harness Plugin Mechanism

`dsh-learning-plugin` is an open-source plugin maintained by fengyufengzi, designed to demonstrate the plugin development mechanism of the DeepSeek Harness ecosystem. It registers a `learning_greet` tool that illustrates four core extension points: declaring service dependencies, validating deployment configurations, registering automatic revocation capabilities in the lifecycle, and deriving parameter and output types from schemas. The project includes complete type checking, testing, and release workflows. After installation, the tool can be invoked in a conversation with the `Use learning_greet to greet Ada` command. Note that Harness is in developer preview, so its API may undergo breaking changes; this plugin is intended only for learning and demonstration, and should not be used in production environments.