fix: Fix broken structured output when using $refs in json_schema

[Galunid]

Overview

Fixes #20178

Additional information

$refs in json schema were resolved only for tool calls, now they're also resolved when using response_format

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: Yes, AI debugged the code and wrote the fix, human verified it works, reviewed the change and made cosmetic fixes

[aldehir]

Remove addition to parsers that have no support for response_format.

[Galunid]

@aldehir Thanks for the review, I addressed your comments. Is there a technical reason those other models don't support response_format, or is it because nobody implemented it yet?

[aldehir]

@Galunid, no one has implemented it yet. It shouldn't be hard, but that can be done in separate PRs.

Thanks!

cc @pwilkin