fix: add docs-validate skip directive for Foundry Local code block

The TypeScript snippet contains bootstrap comments and a bare object
literal that isn't standalone-valid TS, same pattern used elsewhere
in the file (e.g. Azure endpoint type confusion examples).

Author: thegovind

docs/auth/byok.md

@@ -257,6 +257,7 @@ provider: {
 
 Use the [Foundry Local SDK](https://github.com/microsoft/Foundry-Local#-integrate-with-your-applications-using-the-sdk) to bootstrap the service and model, then point the Copilot SDK at the local endpoint:
 
+<!-- docs-validate: skip -->
 ```typescript
 // Bootstrap: npm install foundry-local-sdk
 // import { FoundryLocalManager } from "foundry-local-sdk";