SurfaceRelay

MDI-BB84 through q.Swap, against the engine composition it must match

7/7 passed in 1ms

Test	What it does	Result
test_bound_under	y1 from the decoy grid is a BOUND: it sits under mdi_yield's forward-model value, and above half of it.	✅ pass
test_covariance_kept	A q.BellDetector still runs the covariance path, reporting chi and no counting row.	✅ pass
test_explain_labels	explain() labels every quantity, names the measurement, and reports the sifting factor as absent rather than as a number.	✅ pass
test_matches_engine	The swap's rate is qkd._core's from the same forward model, to the last bit.	✅ pass
test_reach_falls	The rate falls with the span and is zero at an 800 km total.	✅ pass
test_reports_bounds	The result carries the announcement gain, its error rate and the three single-photon-pair quantities the decoy grid bounds, all finite.	✅ pass
test_two_misalignments	Key and test basis carry separate misalignments: worsening only the test one lowers the rate and improving only the key one raises it.	✅ pass