fix(n8n): make replacement replay idempotent

packages/n8n-nodes-ndc/test/package-policy.test.cjs

@@ -170,6 +170,39 @@ async function main() {
   assert.equal(externalContract.validateDataProductPublish(replacement).ok, true);
   assert.equal(replacement.batch.mode, 'replace');
   assert.equal(replacement.batch.generationAt, zoneItems[0].json.observedAt);
+  const replacementReplay = contracts.buildPublishPayload(
+    zoneItems,
+    'execution-replay',
+    'workflow-other',
+    'node-other',
+    'map.zones.current.v1',
+    0,
+    'replace',
+  );
+  assert.equal(
+    replacementReplay.batch.runId,
+    replacement.batch.runId,
+    'the same complete generation must keep one run identity across executions',
+  );
+  assert.equal(
+    replacementReplay.batch.idempotencyKey,
+    replacement.batch.idempotencyKey,
+    'the same complete generation must replay through the data plane idempotently',
+  );
+  const changedReplacement = contracts.buildPublishPayload(
+    [{ json: { ...zoneItems[0].json, attributes: { display_name: 'Zone 42 changed' } } }],
+    'execution-replay',
+    'workflow-other',
+    'node-other',
+    'map.zones.current.v1',
+    0,
+    'replace',
+  );
+  assert.notEqual(
+    changedReplacement.batch.idempotencyKey,
+    replacement.batch.idempotencyKey,
+    'different content at one declared generation must not alias an accepted replay',
+  );
   const replacementBatch = contracts.buildPublishPayload(
     [{ json: { generationAt: zoneItems[0].json.observedAt, facts: zoneItems.map((item) => item.json) } }],
     'execution-44',
@@ -181,6 +214,7 @@ async function main() {
   );
   assert.deepEqual(replacementBatch.facts, replacement.facts);
   assert.equal(replacementBatch.batch.generationAt, zoneItems[0].json.observedAt);
+  assert.equal(replacementBatch.batch.idempotencyKey, replacement.batch.idempotencyKey);
   const emptyReplacement = contracts.buildPublishPayload(
     [{ json: { generationAt: '2026-07-15T13:00:00.000Z', facts: [] } }],
     'execution-45',