init: add source code from src.zip

src/hooks/useMailboxBridge.ts

@@ -0,0 +1,21 @@
+import { useCallback, useEffect, useMemo, useSyncExternalStore } from 'react'
+import { useMailbox } from '../context/mailbox.js'
+
+type Props = {
+  isLoading: boolean
+  onSubmitMessage: (content: string) => boolean
+}
+
+export function useMailboxBridge({ isLoading, onSubmitMessage }: Props): void {
+  const mailbox = useMailbox()
+
+  const subscribe = useMemo(() => mailbox.subscribe.bind(mailbox), [mailbox])
+  const getSnapshot = useCallback(() => mailbox.revision, [mailbox])
+  const revision = useSyncExternalStore(subscribe, getSnapshot)
+
+  useEffect(() => {
+    if (isLoading) return
+    const msg = mailbox.poll()
+    if (msg) onSubmitMessage(msg.content)
+  }, [isLoading, revision, mailbox, onSubmitMessage])
+}