chore: import upstream snapshot with attribution

tests/unit/compression/ionizerGateSkip.test.ts

@@ -0,0 +1,22 @@
+// tests/unit/compression/ionizerGateSkip.test.ts
+import test from "node:test";
+import assert from "node:assert/strict";
+import { applyStackedCompression } from "../../../open-sse/services/compression/strategySelector.ts";
+import { registerBuiltinCompressionEngines } from "../../../open-sse/services/compression/engines/index.ts";
+import { resetCcrStore } from "../../../open-sse/services/compression/engines/ccr/index.ts";
+
+registerBuiltinCompressionEngines();
+
+// 400-row array; ionizer drops most rows → a numeric/json-key gate would normally REJECT a lossy
+// step. Because ionizer is sampling:true, the fidelity gate must SKIP it and keep the sampled output.
+const bigArray = JSON.stringify(Array.from({ length: 400 }, (_, i) => ({ id: i, port: 8080 + i })));
+
+test("fidelity gate ON skips the ionizer step (sampling) and keeps the sampled output", () => {
+  resetCcrStore();
+  const body = { messages: [{ role: "user", content: bigArray }] };
+  const res = applyStackedCompression(body, [{ engine: "ionizer" }], {
+    fidelityGate: { enabled: true },
+  });
+  const content = (res.body.messages as Array<{ content: string }>)[0].content;
+  assert.match(content, /\[ionizer: kept \d+\/400 rows/);
+});