fix(storm-measure): check BOTH halves of the activation SC, not just the count delta

The SC asks two things of an effort: high run: that it discovered at least
one dimension AND that the dimension list in the output brief is a TRUE
SUPERSET of the interview-derived ones. activationCheck computed
dimensions - dimensions_baseline >= 1 and returned ok on that alone. A
count delta says nothing about membership: a run that dropped two
interview dimensions and appended three discovered ones is +1 and passed
the check while violating the second half outright. Supersetness was
asserted only by Phase 4.5's prose contract that discovery appends -
nothing read it.

The stats record cannot carry the dimension names that would show it
directly: names are free prose, and lib/exporters/field-allowlist.mjs
denies prose by omission (question, project_dir, brief_path are already
excluded for that reason). So the run attests membership with
dimensions_baseline_preserved, a boolean set in a new Phase 4.5 step 5,
and the gate refuses to call activation OK without it. An ABSENT
attestation fails rather than falling back to the old count-only rule -
otherwise legacy rows would keep passing on the defect.

Producer side wired end to end: the record format, the measurement-fields
prose (five fields -> six), the exporter allowlist, the jsonl-schemas
fixture row, and the --activation-check comment in
docs/storm-measurement.md.

Review finding d2786604458207a5a73478cdcb6a54bbdb92141d (MINOR).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LuGhWAbWyRFBFeemfhxoVv

tests/scripts/storm-measure.test.mjs

@@ -24,6 +24,7 @@ import {
   partitionEligible,
   measure,
   decideVerdict,
+  activationCheck,
   ADOPT_THRESHOLD,
   DECLINE_THRESHOLD,
 } from '../../scripts/storm-measure.mjs';
@@ -235,6 +236,73 @@ test('decideVerdict: a null gain is insufficient data, never a decline', () => {
   assert.equal(decideVerdict(0.4, null), 'insufficient-data');
 });
 
+// ---------------------------------------------------------------------------
+// activationCheck — BOTH halves of the SC, not just the count
+//
+// The SC requires that an `effort: high` run discovers at least one dimension
+// AND that the dimension list in the output brief is a TRUE SUPERSET of the
+// interview-derived ones. activationCheck only computed dimensions -
+// dimensions_baseline >= 1, so a run that replaced two interview dimensions with
+// three discovered ones passed the check while violating the SC's second half.
+// Supersetness was asserted only by Phase 4.5's prose contract that discovery
+// appends; nothing read it.
+//
+// The stats record carries counts, not names — names are free prose and
+// field-allowlist.mjs denies prose by omission — so the run attests membership
+// with a low-cardinality boolean instead, and the gate refuses to call
+// activation OK without it.
+// ---------------------------------------------------------------------------
+function highRun(over = {}) {
+  return JSON.stringify({
+    ts: '2026-08-12T00:00:00.000Z',
+    effort: 'high',
+    unique_sources: 13,
+    dimensions: 8,
+    dimensions_baseline: 5,
+    conv_turns: 3,
+    empty_turns: 0,
+    dimensions_baseline_preserved: true,
+    ...over,
+  });
+}
+
+test('activationCheck: discovery plus a preserved baseline is activation', () => {
+  const r = activationCheck(parseStats(jsonl(highRun())).records);
+  assert.equal(r.ok, true);
+  assert.equal(r.discovered_dimensions, 3);
+  assert.equal(r.dimensions_baseline_preserved, true);
+});
+
+test('activationCheck: a REPLACED baseline is not activation, however many were discovered', () => {
+  const r = activationCheck(parseStats(jsonl(
+    highRun({ dimensions: 8, dimensions_baseline: 5, dimensions_baseline_preserved: false }),
+  )).records);
+  assert.equal(r.ok, false, 'a count delta of +3 says nothing about which dimensions survived');
+  assert.match(r.reason, /superset|baseline/i);
+});
+
+test('activationCheck: a run that does not attest baseline membership cannot pass', () => {
+  const rec = JSON.parse(highRun());
+  delete rec.dimensions_baseline_preserved;
+  const r = activationCheck(parseStats(jsonl(JSON.stringify(rec))).records);
+  assert.equal(r.ok, false, 'an absent attestation is not an attestation');
+  assert.match(r.reason, /dimensions_baseline_preserved/);
+});
+
+test('activationCheck: no discovery is still not activation even with the baseline preserved', () => {
+  const r = activationCheck(parseStats(jsonl(
+    highRun({ dimensions: 5, dimensions_baseline: 5 }),
+  )).records);
+  assert.equal(r.ok, false);
+  assert.equal(r.discovered_dimensions, 0);
+});
+
+test('activationCheck: no effort:high run at all is reported as such', () => {
+  const r = activationCheck(parseStats(jsonl(...STANDARD)).records);
+  assert.equal(r.ok, false);
+  assert.match(r.reason, /high/);
+});
+
 // ---------------------------------------------------------------------------
 // pre-registration — the thresholds are the doc's, and the doc is committed first
 // ---------------------------------------------------------------------------