修复了多代理并行调用工具时，createProgressCallback 内多个 map 被多 goroutine 并发读写导致的 concurrent map read and map write panic（Issue #142）。通过在闭包内增加 sync.Mutex 串行化状态更新，消除进程崩溃风险；对外接口、SSE 事件与用户交互不变，并补充了 -race 并发测试。
Fixed a fatal concurrent map read and map write panic (Issue #142) when Eino ran multiple tools in parallel and concurrently invoked the progress callback in createProgressCallback. A per-callback sync.Mutex now serializes access to shared maps and aggregation state, preventing crashes without changing APIs, SSE events, or user-facing behavior; a concurrent -race test was added for regression coverage.