DecoySource

The source-model register: the ideal source is the default, and the three source-side idealisations refuse by name

3/3 passed in 0ms

Test	What it does	Result
test_default_ideal	Omitting source, passing None and passing "ideal" give identical results.	✅ pass
test_refusals_direction	Every refusal states the direction of the error it prevents.	✅ pass
test_reject_sources	Every entry point refuses the discrete-phase, intensity-error and correlated sources, and an unknown name lists the register rather than falling back to the ideal source.	✅ pass