fix: preserve inherited fork context and live history attachments

packages/protocol/src/chat-history.ts

@@ -0,0 +1,9 @@
+/** Remove the fork prompt envelope while preserving the snapshot body verbatim. */
+export function extractChatHistoryBody(text: string): string {
+  const bodyStart = text.indexOf("\n\n");
+  return text.startsWith("<chat-history-summary>\n") &&
+    text.endsWith("\n</chat-history-summary>") &&
+    bodyStart !== -1
+    ? text.slice(bodyStart + 2, -"\n</chat-history-summary>".length)
+    : text;
+}