feat(migration): add lock heartbeats, predictive dry-run planning, and stricter ledger option validation

test/test.mongoledger.ts

@@ -74,6 +74,26 @@ tap.test('MongoLedger: expired lock can be stolen', async () => {
   expect(got2).toBeTrue();
 });
 
+tap.test('MongoLedger: holder can renew lock before expiry', async () => {
+  const ledger = new MongoLedger(db, 'renew-test');
+  await ledger.init();
+
+  const got = await ledger.acquireLock('renew-holder', 20);
+  expect(got).toBeTrue();
+
+  await new Promise((r) => setTimeout(r, 10));
+  const renewed = await ledger.renewLock('renew-holder', 40);
+  expect(renewed).toBeTrue();
+
+  await new Promise((r) => setTimeout(r, 25));
+  const stolenEarly = await ledger.acquireLock('other-holder', 40);
+  expect(stolenEarly).toBeFalse();
+
+  await new Promise((r) => setTimeout(r, 25));
+  const stolenLate = await ledger.acquireLock('other-holder', 40);
+  expect(stolenLate).toBeTrue();
+});
+
 tap.test('cleanup: close shared db', async () => {
   await cleanup();
 });