fix: respond to PTY cursor queries

src/agents/pty-dsr.test.ts

@@ -0,0 +1,15 @@
+import { expect, test } from "vitest";
+
+import { buildCursorPositionResponse, stripDsrRequests } from "./pty-dsr.js";
+
+test("stripDsrRequests removes cursor queries and counts them", () => {
+  const input = "hi\x1b[6nthere\x1b[?6n";
+  const { cleaned, requests } = stripDsrRequests(input);
+  expect(cleaned).toBe("hithere");
+  expect(requests).toBe(2);
+});
+
+test("buildCursorPositionResponse returns CPR sequence", () => {
+  expect(buildCursorPositionResponse()).toBe("\x1b[1;1R");
+  expect(buildCursorPositionResponse(12, 34)).toBe("\x1b[12;34R");
+});