test(ultraplan-local): add plan-determinism + review-determinism synthetic fixtures (SC7 floor)

Adds 6 files in tests/synthetic/ exercising the determinism pipeline at the
SC7 brief floor (Jaccard >= 0.833). Plan fixture pair: 40 step titles each
with 38 shared (Jaccard 0.905). Review fixture pair: 30 finding-IDs each
with 28 shared (Jaccard 0.875). Reuses lib/parsers/jaccard.mjs +
lib/parsers/finding-id.mjs.

The new pair coexists with tests/lib/review-determinism.test.mjs which
holds the older SC4 (0.70) floor against tests/fixtures/ultrareview/.
The lower floor protects pipeline regressions; the higher floor anchors
the speedup brief's determinism aspiration.

[skip-docs]

plugins/ultraplan-local/tests/synthetic/plan-determinism.test.mjs

@@ -0,0 +1,63 @@
+// tests/synthetic/plan-determinism.test.mjs
+// SC7 plan-determinism floor — Jaccard pipeline test.
+//
+// Reads two synthetic plan-run fixtures and asserts that
+// jaccardSimilarity(stepsTokens(planA), stepsTokens(planB)) >= 0.833.
+//
+// This exercises the determinism pipeline (parser + jaccard) on a known
+// input pair. It does NOT measure real-LLM determinism — that is deferred
+// to a future run of the pipeline against examples/01-add-verbose-flag/.
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { readFileSync } from 'node:fs';
+import { join, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { jaccardSimilarity } from '../../lib/parsers/jaccard.mjs';
+import { parseDocument } from '../../lib/util/frontmatter.mjs';
+
+const HERE = dirname(fileURLToPath(import.meta.url));
+const ROOT = join(HERE, '..', '..');
+
+const SC7_THRESHOLD = 0.833;
+
+function loadSteps(rel) {
+  const text = readFileSync(join(ROOT, rel), 'utf-8');
+  const doc = parseDocument(text);
+  assert.ok(doc.valid, `frontmatter of ${rel} did not parse: ${(doc.errors || []).map(e => e.message).join(', ')}`);
+  const steps = doc.parsed.frontmatter && doc.parsed.frontmatter.steps;
+  assert.ok(Array.isArray(steps), `frontmatter.steps of ${rel} is not an array`);
+  return steps;
+}
+
+test('plan determinism — Jaccard of synthetic plan-run-A vs plan-run-B meets SC7 threshold (0.833)', () => {
+  const a = loadSteps('tests/synthetic/plan-run-A.md');
+  const b = loadSteps('tests/synthetic/plan-run-B.md');
+  const sim = jaccardSimilarity(a, b);
+  assert.ok(
+    sim >= SC7_THRESHOLD,
+    `jaccardSimilarity(stepsTokens(planA), stepsTokens(planB)) = ${sim} < ${SC7_THRESHOLD} (SC7 floor). ` +
+    `Fixtures may have drifted — re-tune step titles to restore the overlap.`,
+  );
+});
+
+test('plan determinism — both fixtures contain at least 30 unique step titles', () => {
+  for (const rel of ['tests/synthetic/plan-run-A.md', 'tests/synthetic/plan-run-B.md']) {
+    const steps = loadSteps(rel);
+    assert.ok(
+      new Set(steps).size >= 30,
+      `${rel}: < 30 unique step titles (got ${new Set(steps).size}). Synthetic fixtures must reflect a substantial plan.`,
+    );
+  }
+});
+
+test('plan determinism — no duplicate step titles within run', () => {
+  for (const rel of ['tests/synthetic/plan-run-A.md', 'tests/synthetic/plan-run-B.md']) {
+    const steps = loadSteps(rel);
+    assert.strictEqual(
+      new Set(steps).size,
+      steps.length,
+      `${rel}: contains duplicate step titles (${steps.length} entries vs ${new Set(steps).size} unique)`,
+    );
+  }
+});