dsh-backstory: Tracing the "Past and Present" of Code Lines

`dsh-backstory` is a plugin for DeepSeek Harness designed to explain the intent and context of code. By integrating Git history with agent session logs, it provides functional descriptions, historical traceability, and agent provenance at the line level. The plugin supports installation and natural-language interaction, and includes features such as drift-resistant attribution and sensitive-data redaction, helping developers quickly understand code purpose and maintain legacy code.