Fold latitude angles correctly across complete turns

[xiehuanyi]

wrap_mpi2_pi2() returns latitude angles outside its documented [-pi/2, pi/2] range after complete turns: wrap_mpi2_pi2(2*pi) currently returns -2*pi, and 3*pi/2 is left unchanged.

Reduce complete turns while preserving the sign and precision of small angles, then reflect the remaining angle about the poles. Scalar/vector return behavior is unchanged, and the general angle_wrap(..., mode="-pi/2:pi/2") dispatcher receives the same correction.

Regression tests cover positive/negative complete and half turns from -4pi through4pi, scalar/vector forms, the dispatcher, both sides of each pole, exact1e-16 angles and empty vectors. The multiple-turn regression fails before the fix. All20 vector tests pass after it; the broader base suite passes149 tests with1 skip and5 existing warnings. The repository-pinned Black23.10.0 and git diff --check pass.

Prepared with AI assistance.

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