@spec call(map(), map()) :: map()

Builds the canonical Mobus.Stepwise.Projection from the current runtime.

This is an ALF pipeline stage. Computes the projection struct containing all information needed for UI rendering: current state, available events, UI descriptor, artifacts, blocked reasons, subscriptions, errors, and trace.

Available events are derived from the step's position in the ordered step list:

• First step: [:next]
• Last step: [:back]
• Middle steps: [:back, :next]

Parameters

• event — pipeline event map with :spec and :runtime
• opts — ALF stage options (unused)

Returns

• Updated event map with %Mobus.Stepwise.Projection{} in both event.runtime.projection and event.projection.