Update tests to properly wait for async file upload operations:
- Use vi.waitFor() to wait for async upload completion in success case
- Use vi.waitFor() to wait for error message in cross-conversation case
- Add setTimeout delay for decline case to ensure async handler completes
- Adjust assertion order to match new execution flow (invokeResponse first)
The tests were failing because the file upload now happens asynchronously
after sending the invokeResponse, so we need to explicitly wait for the
async operations to complete before making assertions.
ecbb3bcc1a