[BOT ISSUE] OpenAI: add missing `chat-latest` model

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Missing model

The OpenAI chat-latest model alias is not present in the proxy model catalog (packages/proxy/schema/model_list.json).

Model IDs to add

Model ID	Provider(s)	Format	Flavor
chat-latest	openai, azure	openai	chat

Details

chat-latest was released on May 5, 2026 as a rolling snapshot alias that points to the latest Instant model currently used in ChatGPT (currently GPT-5.5 Instant). This follows the existing pattern of versioned *-chat-latest aliases already in the catalog (gpt-5.3-chat-latest, gpt-5.2-chat-latest, gpt-5.1-chat-latest, gpt-5-chat-latest), but is the first version-agnostic rolling alias.

On Azure, the equivalent deployment name is gpt-chat-latest.

Suggested entry

"chat-latest": {
  "format": "openai",
  "flavor": "chat",
  "multimodal": true,
  "input_cost_per_mil_tokens": 5,
  "output_cost_per_mil_tokens": 30,
  "input_cache_read_cost_per_mil_tokens": 0.5,
  "displayName": "GPT Chat Latest",
  "reasoning": true,
  "max_input_tokens": 1050000,
  "max_output_tokens": 128000,
  "available_providers": [
    "openai",
    "azure"
  ]
}

Pricing matches gpt-5.5 ($5/1M input, $30/1M output, $0.50/1M cached input) since chat-latest currently points to GPT-5.5 Instant.

Verification checklist

• Cross-source: Model ID confirmed in OpenAI API changelog (May 5, 2026) and Azure/Microsoft Foundry models documentation
• Recent commits: Not covered by any recent commit to model_list.json
• ID format: Follows OpenAI's alias naming convention; Azure variant is gpt-chat-latest
• Existing issues: No existing issue covers this model ID