DeepSeek Harness Plugin: dsh-handoff - Deterministic Markdown Export for Session Handoff

`dsh-handoff` is a DSH plugin that automatically generates deterministic Markdown handoff documents during multi-turn sessions. It does not call an LLM; instead, it organizes goals, completed or pending tasks, key files, and statistics based on the session event stream. The plugin includes path-fencing security constraints and fallback strategies, making it suitable for quickly handing over workflow progress to a successor at session end or during context switching.