AI Transport: Add a guide for token streaming using OpenAI SDK

This guide provides a concrete example of how to implement the
message-per-token pattern that Mike documented (the one linked to in
this guide).

I initially got Claude to generate this but replaced a fair chunk of its
output. I trusted that its prose is consistent with our tone of voice
and AI Transport marketing position (whether mine is, I have no idea)
and in general trusted its judgements about how to structure the
document. I would definitely welcome opinions on all of the above,
especially from those familiar with how we usually write docs.

I have tried to avoid repeating too much content from the
message-per-token page and have in particular not tried to give an
example of hydration since it seems like a provider-agnostic concept.

Author: lawrence-forooghian

src/data/nav/aitransport.ts

@@ -27,6 +27,15 @@ export default {
         },
       ],
     },
+    {
+      name: 'Guides',
+      pages: [
+        {
+          name: 'Using the OpenAI SDK',
+          link: '/docs/guides/ai-transport/openai-sdk',
+        },
+      ],
+    },
   ],
   api: [],
 } satisfies NavProduct;