feat(web): wire up MCP task support — Tasks screen, Run-as-task, status toasts (#1422) (#1424)

Wires the ported Tasks screen + core task subsystem through App.tsx: sticky Clear Completed, cancel/refresh error toasts, core-side per-task progress correlation, Run-as-task on the Tools screen (gated on server support), per-server Task TTL, and live task-status toasts.

core/react/useManagedRequestorTasks.ts

@@ -10,6 +10,7 @@ import type { TypedEventGeneric } from "../mcp/typedEventTarget.js";
 export interface UseManagedRequestorTasksResult {
   tasks: Task[];
   refresh: () => Promise<Task[]>;
+  clearCompleted: () => void;
 }
 
 /**
@@ -54,5 +55,9 @@ export function useManagedRequestorTasks(
     return next;
   }, [client, managedRequestorTasksState]);
 
-  return { tasks, refresh };
+  const clearCompleted = useCallback((): void => {
+    managedRequestorTasksState?.clearCompleted();
+  }, [managedRequestorTasksState]);
+
+  return { tasks, refresh, clearCompleted };
 }