feat(go): add 100k ingest hardening baseline

go/vehicle-gateway/cmd/gateway/main_test.go

@@ -46,6 +46,16 @@ func TestGatewayConfiguresIdentityLookupCacheTTL(t *testing.T) {
 	}
 }
 
+func TestGatewayDefaultsTo100KConnectionCeiling(t *testing.T) {
+	source, err := os.ReadFile("main.go")
+	if err != nil {
+		t.Fatalf("read main.go: %v", err)
+	}
+	if !strings.Contains(string(source), `envInt("TCP_MAX_CONNECTIONS", 120_000)`) {
+		t.Fatal("gateway should default TCP_MAX_CONNECTIONS to a 100K-ready ceiling")
+	}
+}
+
 func TestNATSSinkConfigFromEnvDefaultsToGoSubjects(t *testing.T) {
 	t.Setenv("NATS_URL", "nats://172.17.111.56:4222")