fix(openai-codex): reset invalid model selection

[hannesrudolph]

Summary

Fixes the settings model dropdown retaining a stale model ID when switching providers (notably when creating/selecting OpenAI - ChatGPT Plus/Pro). Also expands the available OpenAI Codex (ChatGPT subscription) model catalog.

Changes

• Added additional ChatGPT Plus/Pro model IDs to the OpenAI Codex provider catalog in packages/types/src/providers/openai-codex.ts.
• Added provider handler coverage for OpenAI Codex model selection + default fallback in src/api/providers/__tests__/openai-codex.spec.ts.
• Updated provider switch logic so the model is reset to a valid default when the previous model isn't available on the newly selected provider in webview-ui/src/components/settings/ApiOptions.tsx.
• Added UI regression test for anthropic -> openai-codex resetting the model to openAiCodexDefaultModelId in webview-ui/src/components/settings/__tests__/ApiOptions.spec.tsx.

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Important

Fixes model dropdown issue when switching providers and expands OpenAI Codex model catalog.

• Behavior:
  • Fixes model dropdown retaining invalid model ID when switching providers in ApiOptions.tsx.
  • Expands OpenAI Codex model catalog with new model IDs in openai-codex.ts.
• Tests:
  • Adds test for resetting model to default when switching to openai-codex in ApiOptions.spec.tsx.
  • Adds provider handler test for model selection and default fallback in openai-codex.spec.ts.

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