feat: support subtasks

frontend/src/core/tasks/context.tsx

@@ -0,0 +1,46 @@
+import { createContext, useCallback, useContext, useState } from "react";
+
+import type { Subtask } from "./types";
+
+export interface SubtaskContextValue {
+  tasks: Map<string, Subtask>;
+}
+
+export const SubtaskContext = createContext<SubtaskContextValue>({
+  tasks: new Map(),
+});
+
+export function SubtasksProvider({ children }: { children: React.ReactNode }) {
+  const [tasks] = useState<Map<string, Subtask>>(new Map());
+  return (
+    <SubtaskContext.Provider value={{ tasks }}>
+      {children}
+    </SubtaskContext.Provider>
+  );
+}
+
+export function useSubtaskContext() {
+  const context = useContext(SubtaskContext);
+  if (context === undefined) {
+    throw new Error(
+      "useSubtaskContext must be used within a SubtaskContext.Provider",
+    );
+  }
+  return context;
+}
+
+export function useSubtask(id: string) {
+  const { tasks } = useSubtaskContext();
+  return tasks.get(id);
+}
+
+export function useUpdateSubtask() {
+  const { tasks } = useSubtaskContext();
+  const updateSubtask = useCallback(
+    (task: Partial<Subtask> & { id: string }) => {
+      tasks.set(task.id, { ...tasks.get(task.id), ...task } as Subtask);
+    },
+    [tasks],
+  );
+  return updateSubtask;
+}

frontend/src/core/tasks/index.ts

@@ -0,0 +1 @@
+export * from "./types";

frontend/src/core/tasks/types.ts

@@ -0,0 +1,9 @@
+export interface Subtask {
+  id: string;
+  status: "in_progress" | "completed" | "failed";
+  subagent_type: string;
+  description: string;
+  prompt: string;
+  result?: string;
+  error?: string;
+}