Plan provider: the workflow-authoring surface (plan.*) #856

Epic: #815 — Providers

The plan provider (pkg/op/provider/plan) is the surface a workflow is authored through: plan.assemble_definition, plan.save_definition / plan.load_definition, plan.gather, plan.choose, plan.variable, plan.item, plan.origin, and the run entry points. Every provider is a feature under the Providers epic (ruled 2026-09-04); this is the plan provider's, filed 2026-09-07 when a defect in plan.variable had no feature to file under.

Spec: docs/architecture/3.5.3-plan-provider.md

Plan and design documents