Type inference on `filterItems` when using type predicates

Follow-up to #867, which added type-predicate narrowing to findItem.

filterItems still uses the plain ArrayRequirement and returns the input type.

import * as v from 'valibot';

type Animal = 'cat' | 'dog';
const isAnimal = (x: string): x is Animal => x === 'cat' || x === 'dog';

const schema = v.pipe(
  v.array(v.string()),
  v.filterItems(isAnimal),
);

v.parse(schema, ['apple', 'cat', 'screw']);
// inferred: string[] — want: Animal[]

Desired: when the operation is a type guard (item) => item is T, type the action BaseTransformation<TInput, T[], never>, mirroring Array.prototype.filter's overload.

ArrayRequirement$1 (the guard-capable requirement from #867) already exists, so this is mostly wiring.

Workaround today:

v.pipe(v.array(v.string()), v.transform((a) => a.filter(isAnimal)));

Assisted-by: Claude:claude-sonnet-5