Zen: add codex max

Author: Frank

packages/web/src/content/docs/zen.mdx

@@ -66,6 +66,7 @@ You can also access our models through the following API endpoints.
 | ----------------- | ----------------- | ------------------------------------------------ | --------------------------- |
 | GPT 5.1           | gpt-5.1           | `https://opencode.ai/zen/v1/responses`           | `@ai-sdk/openai`            |
 | GPT 5.1 Codex     | gpt-5.1-codex     | `https://opencode.ai/zen/v1/responses`           | `@ai-sdk/openai`            |
+| GPT 5.1 Codex Max | gpt-5.1-codex-max | `https://opencode.ai/zen/v1/responses`           | `@ai-sdk/openai`            |
 | GPT 5             | gpt-5             | `https://opencode.ai/zen/v1/responses`           | `@ai-sdk/openai`            |
 | GPT 5 Codex       | gpt-5-codex       | `https://opencode.ai/zen/v1/responses`           | `@ai-sdk/openai`            |
 | GPT 5 Nano        | gpt-5-nano        | `https://opencode.ai/zen/v1/responses`           | `@ai-sdk/openai`            |
@@ -123,6 +124,7 @@ We support a pay-as-you-go model. Below are the prices **per 1M tokens**.
 | Gemini 3 Pro (> 200K tokens)      | $4.00  | $18.00 | $0.40       | -            |
 | GPT 5.1                           | $1.07  | $8.50  | $0.107      | -            |
 | GPT 5.1 Codex                     | $1.07  | $8.50  | $0.107      | -            |
+| GPT 5.1 Codex Max                 | $1.25  | $10.00 | $0.125      | -            |
 | GPT 5                             | $1.07  | $8.50  | $0.107      | -            |
 | GPT 5 Codex                       | $1.07  | $8.50  | $0.107      | -            |
 | GPT 5 Nano                        | Free   | Free   | Free        | -            |