Commit 2025-09-29 15:10 10d128b5

feat(NumberField/IsCM): compute the index of the subgroup of real units (#26108) This PR continues the work from #23694. We prove that the index of the subgroup of the units of a CM-field generated by the real units and the roots of unity is 1 or 2 and give an equivalent condition for it to be equal to 2.