dsh-timestamp: Timestamp Conversion Tool

`dsh-timestamp` is a Node.js plugin for DeepSeek Harness designed to simplify how agents handle time. It provides two core tools: `timestamp_convert`, which supports mutual conversion among Unix time, ISO 8601, and relative time, and `timestamp_now`. After installation, it needs to be configured and enabled in `package.json`, and can then be called directly within a session. Since the plugin runs code locally, we recommend reviewing the source code in sensitive scenarios.