Fix model version format in agent configuration

[asnewman]

model: anthropic("claude-opus-4.8") results in the following error message:

Error
  MODEL_CALL_FAILED: model: claude-opus-4.8 was not found. Did you mean claude-opus-4-8?

Switching to 4-8 fixes it.

[vercel]

@asnewman is attempting to deploy a commit to the Vercel Team on Vercel.

A member of the Team first needs to authorize it.

[vercel]

Additional Suggestion:

User-facing setup instruction recommends anthropic("claude-opus-4.8") with the dotted Gateway model id, which the direct @ai-sdk/anthropic provider rejects with MODEL_CALL_FAILED: model not found.

[AndrewBarba]

Thanks a lot we'll take a look at this Monday. We're just wrapping up some plumbing on our side so we can officially accept outside contributions, safely run CI etc.