docs(middleware): cross-link the Fundamentals section now that it is merged

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: ankur-arch

apps/docs/content/docs/orm/next/extensions/using-extensions.mdx

@@ -117,6 +117,7 @@ For a working project per extension, see the runnable examples: [pgvector](https
 
 ## See also
 
+- [Advanced queries](/orm/next/fundamentals/advanced-queries): the SQL query builder, where extension operations like `cosineDistance` appear
 - [How middleware works](/orm/next/middleware/how-middleware-works) for wrapping queries rather than adding database capabilities
 - [Quickstart with PostgreSQL](/next/quickstart/postgresql) to set up a project to add extensions to
 - [Prisma Next overview](/orm/next) for the contract-first model extensions plug into

apps/docs/content/docs/orm/next/middleware/how-middleware-works.mdx

@@ -116,5 +116,6 @@ Projects scaffolded with `create-prisma` install Prisma Next skills for your cod
 ## See also
 
 - [Authoring custom middleware](/orm/next/middleware/authoring-custom-middleware): build and test a query logger step by step
+- [Writing data](/orm/next/fundamentals/writing-data): the mutations that lints and budgets guard
 - [Built-in: budgets](/orm/next/middleware/built-in-budgets), [Built-in: lints](/orm/next/middleware/built-in-lints), [Built-in: cache](/orm/next/middleware/built-in-cache)
 - [Using extensions](/orm/next/extensions/using-extensions) for adding database capabilities rather than wrapping queries