fix(dashboard): address ELK layout review feedback

What: Fix three non-blocking issues from PR #232 review.

Why: Code quality — unhandled promise rejection risk, type safety,
and project convention compliance.

Changes:
- packages/workflow-dashboard/src/components/workflow-graph/types.ts:
  add elkLabelX/elkLabelY fields to ConditionEdgeData type (number | null,
  not optional — per project no-optional-properties rule)
- packages/workflow-dashboard/src/components/workflow-graph/use-layout.ts:
  remove 'as ConditionEdgeData' type assertion (now unnecessary),
  add .catch() to computeLayout promise
- packages/workflow-dashboard/src/components/workflow-graph/condition-edge.tsx:
  remove redundant inline type extension, use ConditionEdgeData directly

Ref: PR #232 review comments

packages/workflow-dashboard/src/components/workflow-graph/condition-edge.tsx

@@ -20,7 +20,7 @@ export function ConditionEdge(props: EdgeProps) {
     data,
     markerEnd,
   } = props;
-  const edgeData = data as (ConditionEdgeData & { elkLabelX?: number | null; elkLabelY?: number | null }) | undefined;
+  const edgeData = data as ConditionEdgeData | undefined;
   const isFallback = edgeData?.isFallback ?? false;
   const isSelfLoop = source === target;
 

packages/workflow-dashboard/src/components/workflow-graph/types.ts

@@ -21,6 +21,8 @@ export type ConditionEdgeData = {
   condition: string;
   conditionDescription: string | null;
   isFallback: boolean;
+  elkLabelX: number | null;
+  elkLabelY: number | null;
   [key: string]: unknown;
 };
 

packages/workflow-dashboard/src/components/workflow-graph/use-layout.ts

@@ -99,7 +99,7 @@ function buildEdge(e: WorkflowGraphEdge, elkEdgeMap: Map<string, ElkExtendedEdge
       isFallback,
       elkLabelX: labelX,
       elkLabelY: labelY,
-    } as ConditionEdgeData,
+    },
   };
 }
 
@@ -195,9 +195,16 @@ export function useLayout(input: LayoutInput): LayoutResult {
       roles: JSON.parse(roleJson) as Record<string, { description: string }>,
       nodeStates: input.nodeStates,
     };
-    computeLayout(parsed).then((result) => {
+    computeLayout(parsed)
-      if (!cancelled) setLayout(result);
+      .then((result) => {
-    });
+        if (!cancelled) setLayout(result);
+      })
+      .catch((err: unknown) => {
+        if (!cancelled) {
+          // biome-ignore lint/suspicious/noConsole: layout error reporting
+          console.error("ELK layout failed:", err);
+        }
+      });
     return () => {
       cancelled = true;
     };