chore(migration): standalone SC2/SC7 validation harness

docs/marketplace-polyrepo-migration/migration/40-validate-standalone.test.mjs

@@ -0,0 +1,52 @@
+// Step 6 test — the harness is the test surface: it must PASS a clean extract, FAIL one with a
+// planted tracked state file, and use the glob test form (never a bare dir). Pattern:
+// plugins/voyage/tests/synthetic/*.test.mjs.
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { spawnSync } from 'node:child_process';
+import { mkdtempSync, rmSync, cpSync, writeFileSync, readFileSync } from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+const SCRIPT = path.join(here, '40-validate-standalone.sh');
+const WORK = process.env.WORK || '/tmp/polyrepo-migration';
+
+function harness(key, work) {
+  // Strip the parent test-runner context so the harness's own `node --test` runs un-nested
+  // (otherwise Node emits its IPC subtest format and the test-count label is suppressed).
+  const env = { ...process.env, WORK: work };
+  delete env.NODE_TEST_CONTEXT;
+  return spawnSync('bash', [SCRIPT, key], { encoding: 'utf8', env });
+}
+const git = (dir, args) => spawnSync('git', ['-C', dir, ...args], { encoding: 'utf8' });
+
+test('harness PASSes a clean standalone extract (graceful-handoff)', () => {
+  const r = harness('graceful-handoff', WORK);
+  assert.equal(r.status, 0, `expected PASS exit 0:\n${r.stdout}\n${r.stderr}`);
+  assert.match(r.stdout, /graceful-handoff: PASS \(.*standalone-safe\)/);
+});
+
+test('harness FAILs an extract with a planted tracked state file (SC7)', () => {
+  const tmpWork = mkdtempSync(path.join(os.tmpdir(), 'validate-broken-'));
+  try {
+    const broken = path.join(tmpWork, 'graceful-handoff');
+    cpSync(path.join(WORK, 'graceful-handoff'), broken, { recursive: true });
+    writeFileSync(path.join(broken, 'STATE.md'), '# planted tracked state file\n');
+    assert.equal(git(broken, ['add', '-f', 'STATE.md']).status, 0);
+    assert.equal(git(broken, ['commit', '-m', 'plant tracked STATE.md', '-q']).status, 0);
+
+    const r = harness('graceful-handoff', tmpWork);
+    assert.notEqual(r.status, 0, `expected FAIL (non-zero), got 0:\n${r.stdout}`);
+    assert.match(r.stdout, /graceful-handoff: FAIL/);
+    assert.match(r.stdout, /state-file leak/);
+  } finally {
+    rmSync(tmpWork, { recursive: true, force: true });
+  }
+});
+
+test('harness uses the glob test form, never a bare dir (Node 25 gotcha)', () => {
+  const src = readFileSync(SCRIPT, 'utf8');
+  assert.ok(src.includes('*.test.mjs'), 'harness must reference the glob test form *.test.mjs');
+});