refactor(schema): tighten public contracts (#33771)

packages/schema/src/schema.ts

@@ -11,7 +11,7 @@ export type AbsolutePath = typeof AbsolutePath.Type
 
 export const optional = <S extends Schema.Top>(schema: S) =>
   Schema.optionalKey(schema).pipe(
-    Schema.decodeTo(Schema.optional(schema), {
+    Schema.decodeTo(Schema.optional(Schema.toType(schema)), {
       decode: SchemaGetter.passthrough({ strict: false }),
       encode: SchemaGetter.transformOptional(Option.filter((value) => value !== undefined)),
     }),