Harden hierarchical devtools chart routing

.changeset/gentle-charts-return.md

@@ -0,0 +1,9 @@
+---
+"@typeonce/effect-machine-devtools": patch
+---
+
+Keep charts available for machines that transition between compound states and nested children.
+
+Hierarchy routes now follow the vertical chart direction with stable source, terminal, label, and initial-marker clearance. This includes multi-branch fan-out and returns to a parent's initial configuration.
+
+Parent-origin cues now identify transitions from an ancestor into deeply nested descendants. Transitions owned by parallel states, including child-invocation outcomes, use short local corridors instead of long ELK detours across the container.

packages/devtools/src/internal/browser/chart-layout-policy.ts

@@ -182,10 +182,10 @@ export const makeChartLayoutPolicy = (model: ChartModel): ChartLayoutPolicy => {
       differentAt++
     }
     if (differentAt === sourceLineage.length) {
-      return { direction: "forward", sourceSide: "EAST", targetSide: "EAST" }
+      return { direction: "forward", sourceSide: "SOUTH", targetSide: "NORTH" }
     }
     if (differentAt === targetLineage.length) {
-      return { direction: "backward", sourceSide: "WEST", targetSide: "WEST" }
+      return { direction: "backward", sourceSide: "NORTH", targetSide: "SOUTH" }
     }
 
     const source = nodePolicies.get(sourceLineage[differentAt]!) ?? unreachableNode