CngxFilterOperatorDef

One operator definition: how the operator evaluates an item value against the expression value, an optional default label for the operator picker (resolution order: i18n.operators[key] ?? def.label ?? raw key), and valueless for operators that are complete without an expression value (isEmpty / isNotEmpty family) - a valueless operator is exempt from the empty-value no-op short-circuit.

Register custom definitions through withOperators({...}); the key only appears in a row's operator picker when a FilterFieldDef.operators list or a withDefaultOperators entry names it.