[Bug]: Cannot access Next router in custom container when using NextJS preset with Docs add-on

[karoun]

Describe the bug

I have a wrapping component that accesses next/router for the purpose of registering some event listeners. When I use it as a decorator on my Stories, everything is fine (the @storybook/nextjs mocks kick in), but since the Docs add-on doesn't support decorators, when I use the same wrapping component in a custom container, I get an error (See Reproduction steps).

Reproduction link

https://stackblitz.com/edit/github-bdxeif-nadeqm

Reproduction steps

1. Boot the linked StackBlitz environment
2. Wait for Storybook to finish installing/loading
3. Observe that the "Configure your project" (and all other Docs) display the following error, but Stories do not

Caution

NextRouter was not mounted. https://nextjs.org/docs/messages/next-router-not-mounted

System

Storybook Environment Info:

  System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm <----- active
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @storybook/addon-docs: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/addon-essentials: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/addon-interactions: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/addon-links: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/addon-onboarding: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/blocks: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/nextjs: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/react: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    @storybook/test: ^8.3.0-alpha.1 => 8.3.0-alpha.1 
    storybook: ^8.3.0-alpha.1 => 8.3.0-alpha.1

Additional context

A path to a possible fix would be for the @storybook/next preset to expose the Providers that it uses for the decorators. These could imported in preview.tsx by consumers of the Docs add-on and passed to a custom container.

Needs nextjs and addon: docs labels.