feat(HAI-016): complete Step 1 — create shared AgentSemaphore

packages/engine/src/index.ts

@@ -1,3 +1,4 @@
+export { AgentSemaphore } from "./concurrency.js";
 export { TriageProcessor, type TriageProcessorOptions } from "./triage.js";
 export { TaskExecutor, type TaskExecutorOptions } from "./executor.js";
 export { Scheduler, type SchedulerOptions } from "./scheduler.js";