ModuleMonomLessThan is not a strict comparator for std::sort

Nobody has claimed this yet.

`ModuleMonomLessThan::operator()` in `M2/Macaulay2/e/monomials/monomial-collection.hpp` returns `ModuleMonom::compare(a,b) <= EQ`. `IntsSet::sort` passes it to `std::sort`, which requires a strict weak ordering.

```cpp
int raw[] = {3, 1, 0}; // x
int first[6], second[6];
auto a = monomToModuleMonom(Monom(raw), 1, {first, first+6});
auto b = monomToModuleMonom(Monom(raw), 1, {second, second+6});
ModuleMonomLessThan less;
// Each must be false; each is currently true:
less(a,a);
less(a,b);
less(b,a);
```
This fails irreflexivity even without duplicate entries in a set. Expected comparison should be strict for equal keys.

Reproduced with direct GoogleTest assertions, Debug engine build at c156fdcba4 (Apple Clang 21). No production changes.

### Failing unit-test blocks

- `TEST(MonomialCollections, DISABLED_comparatorIsStrict)` in `M2/Macaulay2/e/unit-tests/MonomialCollectionsTest.cpp`.

These regressions were explicitly run and confirmed to fail against the current implementation. They assert the intended corrected behavior and remain disabled in normal runs until the defect is fixed.

Run from the CMake build directory after building `M2-unit-tests`:

```sh
./Macaulay2/e/M2-unit-tests \
--gtest_also_run_disabled_tests \
--gtest_filter='MonomialCollections.DISABLED_comparatorIsStrict'
```

Inspect ModuleMonomLessThan::operator() in M2/Macaulay2/e/monomials/monomial-collection.hpp, then run the disabled MonomialCollections.DISABLED_comparatorIsStrict test from the CMake build directory. The work is done when the comparator satisfies the strict comparisons asserted by that test and the filtered GoogleTest command passes.

Written by the indexing model from the issue text.