chore: import upstream snapshot with attribution

packages/llmz/vitest.stack-trace-serializer.ts

@@ -0,0 +1,35 @@
+import { SnapshotSerializer } from 'vitest'
+
+const seen = new Set<string>()
+
+const serializer = {
+  serialize(val: string, config, indentation, depth, refs, printer) {
+    const pretty = val
+      .split('\n')
+      .map((line) => {
+        if (/\^{2,}/.test(line)) {
+          return '...' + line.trim()
+        }
+        return line
+      })
+      .join('\n')
+    return printer(pretty, config, indentation, depth, refs)
+  },
+  test(val) {
+    if (typeof val === 'string') {
+      const lines = val.split('\n').filter((line) => !!line.trim().length)
+      const isStack = lines.length > 1 && lines.every((line) => /(\d\d\d \|)|(^\s+\^{2,}$)/i.test(line))
+
+      if (seen.has(val)) {
+        return false
+      }
+
+      seen.add(val)
+      return isStack
+    }
+
+    return false
+  },
+} satisfies SnapshotSerializer
+
+export default serializer as unknown