Assert reopened session ID in DDI integration test

[Copilot]

The reopen-session path should preserve the original session ID, including the ID returned in the DDI response body. The issue requested coverage without expanding emulator behavior.

• Reopen session coverage
  • Added an assertion to test_reopen_session verifying resp.data.sess_id matches the original setup_res.session_id.
  • Keeps the existing emulator behavior unchanged.

assert_eq!(resp.hdr.sess_id, Some(setup_res.session_id));
assert_eq!(resp.data.sess_id, setup_res.session_id);