dsh-file-rename: Bulk File Rename Plugin

`dsh-file-rename` is a Node.js-based DeepSeek Harness plugin that addresses the need for batch file name processing via a plugin. It supports core features such as find/replace, adding prefixes/suffixes, and case conversion, with a dry-run preview mode enabled by default to ensure safe operations. Users can install it using the command `dsh plugin add dsh-file-rename` and then invoke the `rename_files` tool to perform operations. For example, it can batch modify file prefixes or extensions. Given that the plugin involves running local code, it is recommended to review the source code before use.