Add `ne` validator #2190

Job	Run time
Build & verify package	15s
Verify dev env	13s
Check types using supported type checkers	19s
Run doctests & render changelog	21s
Tests on pypy-3.10	24s
Tests & Mypy on 3.14	48s
Tests & Mypy on 3.9	36s
Tests & Mypy on 3.12	55s
Tests & Mypy on 3.10	54s
Tests & Mypy on 3.11	42s
Tests & Mypy on 3.13	49s
Tests & Mypy on 3.15	1m 24s
Ensure everything required is passing for branch protection	3s
Combine & check coverage	1s
	7m 44s

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