dsh-browser-slotpool: Concurrent Browser Session Slot Pool Plugin

`dsh-browser-slotpool` is a plugin for DeepSeek Harness (DSH) that resolves port conflicts and resource interference during concurrent multi-session use through a “slot pool” mechanism. It maintains a fixed number of CDP ports and uses atomic locks together with PID liveness detection to ensure exclusive access and self-healing. It fully delegates to `@playwright/mcp` to guarantee session isolation. After installation, set the environment variable `DSH_BROWSER_LAUNCHER` to point to the launcher path. It is suitable for scenarios that require stable collaboration across multiple browser instances.