feat: auto-flush stats timer, .env.json defaults, expose round-trip+timer tests

tests/src/realtime/expose/expose_test.cpp

@@ -1,4 +1,5 @@
 #include <cassert>
+#include <chrono>
 #include <cstdio>
 #include <thread>
 #include <vector>
@@ -91,6 +92,11 @@ int main() {
     assert(sc.Query(out, false, err));
     assert(out.find("GET") != std::string::npos && out.find("count=1") != std::string::npos);
     assert(sc.Query(out, true, err) && out.front() == '[');
+    sc.StartAutoFlush(std::chrono::seconds(1));
+    sc.Note("POST", 1024, 1024, 1000);
+    std::this_thread::sleep_for(std::chrono::milliseconds(2500));
+    sc.StopAutoFlush();
+    assert(sc.Query(out, false, err) && out.find("POST") != std::string::npos);
     std::remove(db.c_str());
   }
   printf("expose_test PASS\n");