test(08.1-02): pin ARG3-honest gate wording and frozen measurement constants (RED)

MG1/MG2 fail against the current scripts: the optimality gate and the
oracle sweep still describe the binary-under-test in ARG2-era terms and
their decode-failure messages do not name ARG3 or the rebuild command.
MG3 pins the CPU gate's budget/sample constants exactly-once (already
true — stays green).

routing/test/maintainer-scripts.test.mjs

@@ -110,3 +110,54 @@ test("BS5 --check decodes the committed ARG3 fixture green and prints CH facts
   assert.match(out, /chRank length: \d+/, "the rank length must print");
   assert.ok(!/landmark/i.test(out), "--check prints CH facts, never landmark facts");
 });
+
+/* ————— MG — the measurement gates: frozen constants + honest ARG3 wording ————— */
+
+const OPTIMALITY_SCRIPT = path.join(here, "..", "scripts", "measure-optimality-gate.mjs");
+const SWEEP_SCRIPT = path.join(here, "..", "scripts", "measure-astar-oracle-sweep.mjs");
+const CPU_SCRIPT = path.join(here, "..", "scripts", "measure-route-cpu.mjs");
+
+test("MG1 the optimality gate keeps the frozen D-03 constants and honestly names ARG3 when the binary does not decode", () => {
+  const src = readSrc(OPTIMALITY_SCRIPT);
+  assert.equal(
+    countOccurrences(src, "OPTIMALITY_EPSILON_PCT = 0.1"),
+    1,
+    "the ±0.1% epsilon mirror must appear exactly once, unchanged",
+  );
+  assert.equal(
+    countOccurrences(src, "REQUIRED_BASELINE_ARG_VERSION = 1"),
+    1,
+    "the frozen pre-ALT record's argVersion pin must appear exactly once, unchanged",
+  );
+  const code = stripCommentLines(src);
+  assert.ok(code.includes("ARG3"), "the decode-failure message must name ARG3 (the current binary's format)");
+  assert.ok(code.includes("build-road-graph.mjs"), "the failure must name the rebuild command");
+});
+
+test("MG2 the oracle sweep keeps the seeded 200-pair symmetric-compare constants and honestly names ARG3", () => {
+  const src = readSrc(SWEEP_SCRIPT);
+  for (const [constant, occurrences] of [
+    ["SWEEP_PAIR_COUNT = 200", 1],
+    ["SWEEP_SEED = 0x08f1", 1],
+    ["SWEEP_OVERSAMPLE_FACTOR = 3", 1],
+    ["SWEEP_MIN_PAIR_KM = 12", 1],
+    ["ORACLE_EPSILON_S = 1e-6", 1],
+  ]) {
+    assert.equal(countOccurrences(src, constant), occurrences, `"${constant}" must appear exactly ${occurrences} time(s), unchanged`);
+  }
+  const code = stripCommentLines(src);
+  assert.ok(code.includes("ARG3"), "the decode-failure message must name ARG3 (the current binary's format)");
+});
+
+test("MG3 the CPU gate keeps the budget and sample constants exactly once — the 8 ms product budget is the binding pass bar", () => {
+  const src = readSrc(CPU_SCRIPT);
+  for (const [constant, occurrences] of [
+    ["P95_BUDGET_MS = 8", 1],
+    ["ROUTE_COUNT = 25", 1],
+    ["SAMPLE_SEED = 0x06d4", 1],
+    ["EXTENDED_PAIR_COUNT = 100", 1],
+    ["EXTENDED_SEED = 0x08a1", 1],
+  ]) {
+    assert.equal(countOccurrences(src, constant), occurrences, `"${constant}" must appear exactly ${occurrences} time(s), unchanged`);
+  }
+});