Fix dag_elements undefined in run detail template

Add dag_elements to the get_run endpoint render call to match
what the detail.html template expects.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/routers/runs.py

@@ -171,11 +171,42 @@ async def get_run(
                 "media_type": media_type or "application/octet-stream",
             })
 
+        # Build DAG elements for visualization
+        dag_elements = []
+        if plan and plan.get("steps"):
+            node_colors = {
+                "input": "#3b82f6",
+                "effect": "#8b5cf6",
+                "analyze": "#ec4899",
+                "transform": "#10b981",
+                "output": "#f59e0b",
+                "SOURCE": "#3b82f6",
+                "EFFECT": "#8b5cf6",
+                "SEQUENCE": "#ec4899",
+            }
+            for i, step in enumerate(plan["steps"]):
+                step_id = step.get("id", f"step-{i}")
+                dag_elements.append({
+                    "data": {
+                        "id": step_id,
+                        "label": step.get("name", f"Step {i+1}"),
+                        "color": node_colors.get(step.get("type", "effect"), "#6b7280"),
+                    }
+                })
+                for inp in step.get("inputs", []):
+                    dag_elements.append({
+                        "data": {
+                            "source": inp,
+                            "target": step_id,
+                        }
+                    })
+
         templates = get_templates(request)
         return render(templates, "runs/detail.html", request,
             run=run,
             plan=plan,
             artifacts=artifacts,
+            dag_elements=dag_elements,
             active_tab="runs",
         )