feat(trekresearch): emit and export the five STORM measurement fields

tests/hooks/otel-export-textfile.test.mjs

@@ -31,6 +31,25 @@ test('SC #12: stats-sample.jsonl → expected.prom snapshot byte-for-byte match'
     `  node scripts/gen-expected-prom.mjs > tests/fixtures/expected.prom`);
 });
 
+test('Step 9: the four numeric STORM fields are metric families and effort is a label', () => {
+  const expected = readFileSync(join(FIXTURES, 'expected.prom'), 'utf-8');
+  for (const field of ['unique_sources', 'dimensions_baseline', 'conv_turns', 'empty_turns']) {
+    assert.match(
+      expected,
+      new RegExp(`^# TYPE voyage_trekresearch_${field} `, 'm'),
+      `${field} must appear as its own metric family — a numeric that never becomes a metric cannot be measured`,
+    );
+  }
+  // effort is a low-cardinality string: it must ride along as a LABEL, never
+  // as a metric family (a label is what makes high-vs-standard groupable).
+  assert.match(expected, /effort="[a-z]+"/, 'effort must be emitted as a label');
+  assert.doesNotMatch(
+    expected,
+    /^# TYPE voyage_trekresearch_effort /m,
+    'effort must not become a metric family',
+  );
+});
+
 test('empty-input handling: [] returns empty string (no headers)', () => {
   assert.equal(transformToPrometheus([]), '');
   assert.equal(transformToPrometheus(null), '');