dsh-column: Column Formatting

`dsh-column` is a structured data display plugin in the DeepSeek Harness (DSH) ecosystem, maintained by uckkk. It is a pure Node implementation that requires no network requests and is released under the MIT license. Installation requires the `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools` dependencies. The plugin provides column formatting capabilities, allowing registered tools to be invoked during a session to output structured tabular data.