chore: import upstream snapshot with attribution

apps/sim/executor/dag/construction/sentinels.ts

@@ -0,0 +1,38 @@
+import type { BlockType, SentinelType } from '@/executor/constants'
+import type { DAGNode } from '@/executor/dag/builder'
+import type { SentinelSubflowType } from '@/executor/dag/types'
+
+interface SubflowSentinelNodeConfig {
+  id: string
+  subflowId: string
+  subflowType: SentinelSubflowType
+  sentinelType: SentinelType
+  blockType: BlockType
+  name: string
+}
+
+export function createSubflowSentinelNode(config: SubflowSentinelNodeConfig): DAGNode {
+  return {
+    id: config.id,
+    block: {
+      id: config.id,
+      enabled: true,
+      position: { x: 0, y: 0 },
+      metadata: {
+        id: config.blockType,
+        name: config.name,
+      },
+      config: { tool: config.blockType, params: {} },
+      inputs: {},
+      outputs: {},
+    },
+    incomingEdges: new Set(),
+    outgoingEdges: new Map(),
+    metadata: {
+      isSentinel: true,
+      sentinelType: config.sentinelType,
+      subflowId: config.subflowId,
+      subflowType: config.subflowType,
+    },
+  }
+}