feat: decision tree visualization with React Flow + Dagre auto-layout

apps/web/src/app/api/traces/[id]/route.ts

@@ -38,7 +38,44 @@ export async function GET(
       return NextResponse.json({ error: "Trace not found" }, { status: 404 });
     }
 
-    return NextResponse.json({ trace }, { status: 200 });
+    // Transform data to match frontend expectations
+    const transformedTrace = {
+      ...trace,
+      decisionPoints: trace.decisionPoints.map((dp) => ({
+        id: dp.id,
+        type: dp.type,
+        chosenAction: typeof dp.chosen === "string" ? dp.chosen : JSON.stringify(dp.chosen),
+        alternatives: dp.alternatives.map((alt) => (typeof alt === "string" ? alt : JSON.stringify(alt))),
+        reasoning: dp.reasoning,
+        contextSnapshot: dp.contextSnapshot as Record<string, unknown> | null,
+        confidence: null, // Not in schema, default to null
+        timestamp: dp.timestamp.toISOString(),
+        parentSpanId: dp.parentSpanId,
+      })),
+      spans: trace.spans.map((span) => ({
+        id: span.id,
+        name: span.name,
+        type: span.type,
+        status: span.status === "COMPLETED" ? "OK" : span.status === "ERROR" ? "ERROR" : "CANCELLED",
+        startedAt: span.startedAt.toISOString(),
+        endedAt: span.endedAt?.toISOString() ?? null,
+        durationMs: span.durationMs,
+        input: span.input,
+        output: span.output,
+        metadata: (span.metadata as Record<string, unknown>) ?? {},
+        parentSpanId: span.parentSpanId,
+      })),
+      events: trace.events.map((event) => ({
+        id: event.id,
+        type: event.type,
+        name: event.name,
+        timestamp: event.timestamp.toISOString(),
+        metadata: (event.metadata as Record<string, unknown>) ?? {},
+        spanId: event.spanId,
+      })),
+    };
+
+    return NextResponse.json({ trace: transformedTrace }, { status: 200 });
   } catch (error) {
     console.error("Error retrieving trace:", error);
     return NextResponse.json({ error: "Internal server error" }, { status: 500 });