Function deep_resolve_refs 

pub fn deep_resolve_refs(
    schema: &Value,
    openapi_doc: &Value,
    depth: usize,
) -> Value

Recursively resolve all $ref pointers in a schema.

Handles $ref, allOf, anyOf, oneOf, items, prefixItems, properties, patternProperties, additionalProperties, not, and if/then/else. Depth-limited: resolves through depth 16 (cuts off at depth > 16), matching the Python and TypeScript implementations.