List Opportunity Folders

Retrieve the top level of an opportunity's Docs tab: workflow phases, plus any real doc folders that sit at the opportunity root (not nested in another folder or scoped to a phase). Same shape as the project version of this endpoint — opportunities have their own workflow phases too.

To see what's inside a phase or folder, use GET /phases/{phase_instance_id}/contents or GET /folders/{folder_id}/contents — both are addressed by id alone, no opportunity needed in the path.