fix(structured outputs): correct schema coercion for inline ref expansion

[KanchiShimono]

• I understand that this repository is auto-generated and my pull request may not be merged

Changes being requested

Fixes #2024

This PR updates the _ensure_strict_json_schema function so that when a $ref is expanded inline (due to the presence of other fields like description), we recursively re-run the function on the resulting inline object. This ensures additionalProperties: false is correctly applied even if the schema is expanded.

Additionally, new test code has been added to confirm that models with nested references and annotated fields (e.g., Field(description="...")) correctly produce additionalProperties=False for the inline-expanded objects.

Additional context & links

• This addresses scenarios where $ref plus extra properties leads to inline expansion, causing the prior implementation to skip setting additionalProperties: false.
• The newly introduced unit test verifies that models with description fields do not lose their strict schema configuration after the inline expansion.

[RobertCraigie]

Thanks!