Fix RecursionError with mutually recursive models in CLI

[hramezani]

Summary

• Fixes the remaining case from RecursionError with Self-Referential Models in CliApp #781 reported in this comment
• The previous fix (4a98429) only prevented direct self-recursion (Foo -> Foo) by checking m is not model
• This did not handle indirect/mutual recursion where models reference each other through discriminated unions (e.g., B has field Union[A, B, C] and C has field Union[A, B, C], creating a cycle B -> C -> B -> ...)
• Now tracks the full ancestor model_path set through recursion and filters sub-models against all visited ancestors

Test plan

• Added test_cli_mutually_recursive_models covering the exact scenario from the issue comment (discriminated unions with mutually recursive models)
• Existing test_cli_self_referential_model still passes (direct self-recursion)
• Full CLI test suite passes (167 tests)

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