[Firebolt9907]

Summary

Currently, Diffex defaults the model to "gpt-5.5" when using the Codex provider, which was removed from ChatGPT plans around 2 weeks ago. This change replaces the default with GPT 5.6 Terra, which is the best selection for a minimum version bump.

Update model-resolver.ts to use 5.6 Terra for codex

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Reasoning

I'm assuming 5.5 was used as the minimum version, so I just did a minimum version bump, and 5.6 Terra seemed like the best balanced model to replace the selection. If this is meant to be the latest balanced model, it would probably be better to replace this with 6.1 Terra instead, as it got released yesterday.

N/A

Changes

Updated model resolver and tests.

Testing

N/A

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[github-actions]

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