Naming conflict: `anvil/reference.md` and `anvil/reference/` folder

[mablr]

There is a naming conflict between vocs/docs/pages/anvil/reference/ (folder) and vocs/docs/pages/anvil/reference.md (file), which makes the latest not visible in the navigation pane.

I propose to move reference.md into the reference/ folder (e.g., rename to api.mdx) and maybe refactor content in relation to reference/anvil.mdx to avoid duplication and improve structure.

if you find this relevant, I'll make a PR 👍

[newalemon-pixel]

Recovery issue

[onbjerg]

@mablr sgtm

[mablr]

I'll do that 👍