dsh-session-export: DeepSeek Harness Session Export and Compliance Archiving Plugin

The DeepSeek Harness (dsh) plugin `dsh-session-export` is designed to address sensitive information leakage in session exports and provide compliant archiving. It sanitizes session records using a rule-based deterministic engine, removing sensitive data such as API keys and JWTs, and generates verifiable SHA-256 fingerprints. It supports multiple formats, including Markdown, JSONL, and PDF, and provides full archive management, search, and deletion capabilities with audit metadata. The tool is model-agnostic, integrates through tool commands and slash commands, and meets high security and compliance requirements.