dsh-orchestrator: Adding Multi-Agent Orchestration Mode to DeepSeek Harness

dsh-orchestrator is an MIT-licensed orchestration plugin (v0.1.3) for DeepSeek Harness (DSH), designed to optimize multi-agent collaboration through a "master agent + worker mesh" pattern. It replaces conventional prompt conventions or external polling by leveraging the harness's built-in inbox to enable native message exchange between any agents. Core features include: the master agent handles task decomposition and dispatch; workers execute specific tasks and can independently configure models, providers, and thinking intensity (off/high/max). It provides four tool interfaces: `agent_spawn` spawns persistent workers; `agent_send` sends messages to online agents (without blocking for replies); `agent_broadcast` broadcasts