docs: github copilot model enable note (#2741)

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

@@ -356,6 +356,8 @@ To use your GitHub Copilot subscription with opencode:
 :::note
 Some models might need a [Pro+
 subscription](https://github.com/features/copilot/plans) to use.
+
+Some models need to be manually enabled in your [GitHub Copilot settings](https://docs.github.com/en/copilot/how-tos/use-ai-models/configure-access-to-ai-models#setup-for-individual-use).
 :::
 
 1. Run `opencode auth login` and select GitHub Copilot.