dsh-agent-relay: Local Multi-Agent Message Relay for DSH

dsh-agent-relay is an MIT-licensed plugin maintained by Noelune, designed to address secure message interoperability among multiple local agents (such as dsh, Codex, etc.) on the same machine. It achieves relay through a local broker that binds to 127.0.0.1:19121 by default, and ensures authentication security using HMAC-SHA256 signatures, timestamp replay protection, and rate limiting. Core capabilities include lease/ack-based reliable delivery, cursor-based incremental polling, idempotent deduplication, exponential backoff retries, and 7-day TTL message retention. Data persistence defaults to SQLite (requiring Node.js >= 22.5, with fallback to JSONL for lower versions), supporting protocol versions from v1 to v3, where v3