fix: serialize autonomy job leases

src/autonomy/jobs.js

@@ -31,7 +31,15 @@ function leaseNextJob(db, workerId, leaseSeconds = 60, jobTypes = null) {
     `).run(workerId, `+${Math.max(1, Math.floor(leaseSeconds))} seconds`, job.id);
     return updated.changes ? { ...job, status: 'leased', leased_by: workerId } : null;
   });
-  return tx();
+  try {
+    // Acquire the write reservation before selecting. A deferred transaction can
+    // otherwise read a snapshot, lose the writer race, and fail with
+    // SQLITE_BUSY_SNAPSHOT when it attempts the lease update.
+    return tx.immediate();
+  } catch (error) {
+    if (String(error.code || '').startsWith('SQLITE_BUSY')) return null;
+    throw error;
+  }
 }
 
 function completeJob(db, id, workerId) {