refactor: reorganize test structure with directory-based organization

- Reorganize tests into logical directories: basic/, predicates/, extended/, scenarios/, compatibility/, benchmarks/
- Move individual operation tests to appropriate directories maintaining granular testing
- Split advanced predicates into separate files (and_test.go, or_test.go, not_test.go)
- Consolidate benchmark tests into single benchmarks/ directory
- Create unified testutils library for consistent test patterns
- Remove "advanced" prefixes and simplify naming conventions
- Fix all linting issues and ensure code formatting consistency
- Maintain all existing test functionality while improving organization

Author: kaptinlin

codec/json/decode.go

@@ -97,10 +97,14 @@ func OperationToOp(operation map[string]interface{}, options internal.JSONPatchO
 	case "flip":
 		return op.NewOpFlipOperation(path), nil
 	case "inc":
-		incVal, ok := op.ToFloat64(operation["inc"])
-		if !ok {
+		incField, hasInc := operation["inc"]
+		if !hasInc {
 			return nil, ErrIncOpMissingInc
 		}
+		incVal, ok := op.ToFloat64(incField)
+		if !ok {
+			return nil, ErrIncOpInvalidType
+		}
 		return op.NewOpIncOperation(path, incVal), nil
 	case "str_ins":
 		pos, ok := op.ToFloat64(operation["pos"])

codec/json/errors.go

@@ -15,6 +15,8 @@ var (
 
 	// ErrIncOpMissingInc indicates inc operation is missing 'inc' field
 	ErrIncOpMissingInc = errors.New("inc operation missing 'inc' field")
+	// ErrIncOpInvalidType indicates inc operation 'inc' field must be a number
+	ErrIncOpInvalidType = errors.New("inc operation 'inc' field must be a number")
 	// ErrStrInsOpMissingPos indicates str_ins operation is missing 'pos' field
 	ErrStrInsOpMissingPos = errors.New("str_ins operation missing 'pos' field")
 	// ErrStrInsOpMissingStr indicates str_ins operation is missing 'str' field