clang-format: operators break `SortIncludes`

[bersbersbers]

clang-format version 21.1.1

x.h:

using std::a;
using MyLib::operator+;
using std::c;
using std::b;

y.h:

using std::a;
using MyLib::xxx;
using std::c;
using std::b;

clang-format x.h --style=Google:

using std::a;
using MyLib::operator+;
using std::b;
using std::c;

clang-format y.h --style=Google:

using MyLib::xxx;
using std::a;
using std::b;
using std::c;

Note how includes are fully sorted only in y.h (which is as I would expect it) but not in x.h (where I would have expected sorting as well).

[llvmbot]

@llvm/issue-subscribers-clang-format

Author: None (bersbersbers)

``` clang-format version 21.1.1 ```

x.h:

using std::a;
using MyLib::operator+;
using std::c;
using std::b;

y.h:

using std::a;
using MyLib::xxx;
using std::c;
using std::b;

clang-format x.h --style=Google:

using std::a;
using MyLib::operator+;
using std::b;
using std::c;

clang-format y.h --style=Google:

using MyLib::xxx;
using std::a;
using std::b;
using std::c;

Note how includes are fully sorted only in y.h (which is as I would expect it) but not in x.h (where I would have expected sorting as well).