fix(openapi-typescript): emit \ as optional property (#2664)

[EduardF1]

Changes

Fixes #2664.

The generated $defs container is currently emitted as a required property of the surrounding object type. Because $defs only hosts reusable subschema definitions (it never appears in actual request/response data), requiring it forces consumers to supply a $defs value whenever they use the generated schema as an input type, producing spurious type errors.

This change marks the emitted $defs property as optional (adds a ? question token). $refs that index into $defs (e.g. components["schemas"]["OtherObject"]["$defs"]["nestedDef"]) continue to resolve, because indexed-access types work identically on optional properties — so ref resolution is fully preserved.

Before

Object: {
    rootDef?: $defs["StringType"];
    $defs: {            // required — must be supplied on input
        hasDefs: boolean;
    };
};

After

Object: {
    rootDef?: $defs["StringType"];
    $defs?: {           // optional — no longer required on input
        hasDefs: boolean;
    };
};

How to review

• packages/openapi-typescript/src/transform/schema-object.ts — the emitted $defs PropertySignature now uses QUESTION_TOKEN instead of undefined.
• Existing snapshots in test/transform/schema-object/object.test.ts and test/index.test.ts (including the JSONSchema > $defs are respected case that exercises refs into $defs) updated from $defs: to $defs?:. These assertions only pass with the fix in place.

Tests run

• vitest run test/transform/schema-object/object.test.ts test/index.test.ts → 56 passed
• vitest run test/transform test/discriminators.test.ts test/node-api.test.ts → 194 passed (validated before submission)
• biome check on the changed files → clean

A changeset (openapi-typescript patch) is included.

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Latest commit: 004105f

The changes in this PR will be included in the next version bump.

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Name	Type
openapi-typescript	Patch

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