chore: import upstream snapshot with attribution

tests/unit/compression/eval-selftest.test.ts

@@ -0,0 +1,33 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { runSelfTest, CONTROL_PAIR } from "../../../open-sse/services/compression/eval/judge.ts";
+import type { ModelClient } from "../../../open-sse/services/compression/eval/types.ts";
+
+/** A judge that correctly ranks the control pair (degraded => MATERIALLY_DIFFERS, good => SAME). */
+function correctJudge(): ModelClient {
+  return {
+    async complete(_model, messages) {
+      const u = messages.find((m) => m.role === "user")?.content ?? "";
+      const degraded = u.includes(CONTROL_PAIR.degraded);
+      return { text: degraded ? "VERDICT: MATERIALLY_DIFFERS" : "VERDICT: SAME" };
+    },
+  };
+}
+
+/** A broken judge that always says SAME — must FAIL self-test. */
+function brokenJudge(): ModelClient {
+  return { async complete() { return { text: "VERDICT: SAME" }; } };
+}
+
+describe("judge self-test gate (D-D3)", () => {
+  it("a correct judge passes self-test", async () => {
+    const r = await runSelfTest(correctJudge(), "judge-model");
+    assert.equal(r.passed, true);
+  });
+
+  it("a broken judge (always SAME) fails self-test", async () => {
+    const r = await runSelfTest(brokenJudge(), "judge-model");
+    assert.equal(r.passed, false);
+    assert.match(r.detail, /degraded|control/i);
+  });
+});