[BETA🧪] Create a new funnel in the workspace. This endpoint is in private BETA.

Creating a funnel automatically creates a workflow. You can then add pages to the funnel by creating pages with funnel.funnel_id set to the new funnel's ID (see the Create Page endpoint).

Client flow for building a funnel with pages:

1. POST /api/v2/workspaces/:id/funnels — creates the funnel (workflow auto-created)
2. POST /api/v2/workspaces/:id/pages with { page: { name: "...", funnel: { funnel_id: "<funnel_id>" } } } — creates each page and auto-links it to the funnel
3. POST /api/v2/pages/:page_id/markup with { page_markup: { markup: "<PML string>" } } — applies visual content (PML markup) to each page

The internal step/workflow wiring is handled automatically — API clients never need to manage workflows or steps directly.