Way to add error with custom value path

In rule handlers Result::addError() is added error message to current key and value path define path into key. Need ability to add error with globally path.

Example:

$result = (new Validator())->validate(
    data: ['a' => 1, 'b' => 2],
    rules: [
        'a' => new Callback(function(){
            $result = new Result();
            $result->addError('message', valuePath: ['b']);
            return $result;
        })
    ],
);

// Errors:
// ['a.b' => ['message']]

Need additional ability add error to key b. May be implement it via adding method addError() to validation context object.

Start by reading Result::addError and the rule-handler validation flow described in the issue, then inspect how value paths are combined. Compare the proposed validation-context approach with the existing API. Done means an error created while validating a can target b directly, producing the requested global path rather than a.b, with behavior verified by tests for the example.