Live testing

Most of the suite is deterministic and free; the part that talks to real Cursor accounts is opt-in, so CI never burns credits by accident:

pytest                    # unit + integration, no network
pytest -m system          # deterministic end-to-end harness, still no vendor calls
pytest -m live            # real account, real spend — needs CURSOR_API_KEY

-m live is for release verification and vendor-behavior changes (a new rate-limit phrasing, a changed completion format). Run it with a bounded budget in the environment (CURSORLOOP_MAX_DOLLARS) so a broken test cannot spend more than pocket change.