ZodObject has all properties optional

For some reason, all inferred types of ZodObject have the properties as optional. This is particularly annoying when extracting a type from a discriminated union.
```ts
const zContentPageNode = z.discriminatedUnion("type", [
z.object({
type: z.literal("component"),
componentVersion: z.string().ulid(),
content: z.record(z.unknown()),
}),
z.object({
type: z.literal("formattedText"),
content: z.record(z.unknown()),
}),
]);

type zContentPageNode = z.infer;
type ComponentNode = Extract;
// expect: { type: "component", componentVersion: string, content: Record }
// actual: never
```

Without `chanfana`, this works as expected

TypeScript version 5.6.3
zod 3.23.8
hono 4.6.9
chanfana 2.1.0

Reproduce the supplied TypeScript example with chanfana 2.1.0 and compare the inferred ZodObject and discriminated-union types with and without chanfana. Trace the schema/type entry points used by chanfana; done when required properties are preserved and Extract produces the expected ComponentNode type.

Written by the indexing model from the issue text.