feat: add gpt-5.2-codex model

[cyhhao]

Background

OpenAI’s official Codex CLI ships gpt-5.2-codex as a first-class model preset (see model_presets.rs) and uses it as the default ChatGPT/Codex model (see manager.rs). However, models.dev currently lacks this model entry.

Change

• Add providers/openai/models/gpt-5.2-codex.toml
• Align specs with gpt-5.2 (context window, pricing, knowledge date, etc.)

Notes

• In the Codex CLI preset list, gpt-5.2-codex is marked supported_in_api: false, so this appears to be a Codex/ChatGPT channel model rather than a public API-key model. If the fields should differ, I’m happy to adjust.

Verification

• bun validate

[rekram1-node]

since it isnt available via api it doesnt mae sense to add here rn

[cyhhao]

@rekram1-node But OpenCode has just supported Codex's OAuth authentication. If we don't add it, how can we use this model in this mode?

[rekram1-node]

@cyhhao see here: https://github.com/anomalyco/opencode/blob/b81eca4ebc73279ab2c16fb1ca3291449501729d/packages/opencode/src/plugin/codex.ts#L364