dsh--merge: JSON Deep Merge

`dsh--merge` is an online tool plugin for the DeepSeek Harness (DSH) environment, designed to solve the challenge of merging deeply nested JSON objects. It implements deep merging through a recursive algorithm while preserving the properties of non-target objects, making it suitable for processing complex configurations. To install it, use the `dsh plugin add dsh--merge` command and modify the profile configuration to enable it. Developers should note that the plugin runs locally with the permissions of the current process, and it is recommended to review its source code and license (MIT).