runtime: add execution concurrency limits

apps/admin-api/src/error.rs

@@ -403,6 +403,7 @@ fn runtime_test_failure_code(error: &RuntimeError) -> &'static str {
         RuntimeError::SoapAdapter(_) => "runtime_soap_error",
         RuntimeError::WebsocketAdapter(_) => "runtime_websocket_error",
         RuntimeError::UnsupportedProtocol { .. } => "runtime_protocol_error",
+        RuntimeError::ConcurrencyLimitExceeded { .. } => "runtime_overloaded",
         RuntimeError::InvalidPreparedRequest { .. } => "runtime_request_error",
         RuntimeError::MissingStreamingConfig { .. } => "runtime_streaming_config_error",
         RuntimeError::UnsupportedExecutionMode { .. } => "runtime_streaming_mode_error",
@@ -454,6 +455,10 @@ pub fn runtime_error_context(error: &RuntimeError) -> Option<Value> {
         RuntimeError::UnsupportedProtocol { protocol } => Some(json!({
             "protocol": protocol,
         })),
+        RuntimeError::ConcurrencyLimitExceeded { kind, limit } => Some(json!({
+            "kind": kind,
+            "limit": limit,
+        })),
         _ => None,
     }
 }
@@ -500,6 +505,23 @@ mod tests {
         );
     }
 
+    #[test]
+    fn runtime_test_failure_includes_runtime_overload_context() {
+        let payload = runtime_test_failure(&RuntimeError::ConcurrencyLimitExceeded {
+            kind: "window",
+            limit: 16,
+        });
+
+        assert_eq!(payload["code"], "runtime_overloaded");
+        assert_eq!(
+            payload["context"],
+            json!({
+                "kind": "window",
+                "limit": 16
+            })
+        );
+    }
+
     #[test]
     fn registry_errors_preserve_structured_context_in_api_error() {
         let error = ApiError::from(RegistryError::InvalidAsyncJobTransition {