Add GPT-5.5 support for ChatGPT Plus/Pro

[Mike Hjazeen (mjjjjaazing)]

Summary

• add gpt-5.5 as the first/default ChatGPT Plus/Pro model
• update the ChatGPT Plus/Pro provider template and OAuth fallback default to gpt-5.5
• document GPT-5.5 and its 1.05M context window
• add focused tests for the model list, provider template, and server-side fallback

Validation

• bun test apps/agent/entrypoints/app/ai-settings/models.test.ts apps/agent/lib/llm-providers/providerTemplates.test.ts apps/server/tests/lib/clients/llm/config.test.ts
• bunx biome check apps/agent/entrypoints/app/ai-settings/models.ts apps/agent/entrypoints/app/ai-settings/models.test.ts apps/agent/lib/llm-providers/providerTemplates.ts apps/agent/lib/llm-providers/providerTemplates.test.ts apps/server/src/lib/clients/llm/config.ts apps/server/tests/lib/clients/llm/config.test.ts ../../docs/features/chatgpt-pro-oauth.mdx
• bun run --filter @browseros/server typecheck
• bun run codegen:agent
• bun run --filter @browseros/agent typecheck

OpenAI currently lists gpt-5.5 as the recommended flagship model for complex reasoning and coding, with model ID gpt-5.5 and a 1,050,000 token context window.

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[Mike Hjazeen (mjjjjaazing)]

I have read the CLA Document and I hereby sign the CLA