omdsh-editor: Invoke Local Editor in DeepSeek Harness

The `omdsh-editor` plugin adds split controllers to DeepSeek Harness (DSH), solving the issue of not being able to directly invoke local development environments. It supports opening an editor or terminal directly via the web interface and provides APIs for retrieving editor lists, icons, and launching applications. The plugin detects local applications by scanning macOS apps, Windows executables, or the `PATH` environment variable, and supports custom configuration, though changes require a DSH restart to take effect.