docs: define workflow engine and editor split

docs/CONCEPT.md

@@ -2,9 +2,10 @@
 
 ## Purpose
 
-`govoplan-workflow` is the process orchestration module. It turns a configured
-administrative procedure into state transitions, guards, commands, timers, and
-operator-visible progress.
+The current `govoplan-workflow` package is the process orchestration module. The
+accepted target moves definition/runtime ownership to the headless
+`govoplan-workflow-engine` module and keeps `govoplan-workflow` as the optional
+authoring and inspection surface. See `ENGINE_EDITOR_SPLIT.md`.
 
 Workflow does not own business records. A case, task, file, appointment,
 template, payment, or postbox message remains owned by its domain module.
@@ -193,8 +194,6 @@ Minimum tests:
 
 ## Open Decisions
 
-- Whether to implement BPMN import later or keep a GovOPlaN-native JSON model.
-- How much visual workflow editing belongs in the first WebUI.
 - Whether long-running timers use Celery beat, a module scheduler, or an ops
   scheduler abstraction.
 - How workflow variables are redacted and retained.