The 1000-element stack limit counts the witness elements plus the
elements the script pushes while it runs, so the witness element count
alone does not decide it. This pass computes the second half: the peak
number of elements a satisfaction pushes beyond the witness.
The model is the true peak rather than rust-miniscript's estimate, whose
threshold value is order dependent; where the two differ is recorded in
the differential test and in the package documentation.
