[NEB-247] Show error event in chat UI (#7022)

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---

## PR-Codex overview
This PR introduces error handling for chat responses in the `ChatPageContent` and `chat.ts` files. It adds functionality to display error messages when an error event is received.

### Detailed summary
- Added handling for `"error"` case in `ChatPageContent.tsx` to update messages with error details.
- Implemented parsing of error data in `chat.ts` to extract error code and message.
- Updated `ChatStreamedEvent` type to include an `"error"` event with relevant data structure.

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Author: MananTank

apps/dashboard/src/app/nebula-app/(app)/api/chat.ts

@@ -152,6 +152,24 @@ export async function promptNebula(params: {
         break;
       }
 
+      case "error": {
+        const data = JSON.parse(event.data) as {
+          code: number;
+          error: {
+            message: string;
+          };
+        };
+
+        params.handleStream({
+          event: "error",
+          data: {
+            code: data.code,
+            errorMessage: data.error.message,
+          },
+        });
+        break;
+      }
+
       case "init": {
         const data = JSON.parse(event.data);
         params.handleStream({
@@ -242,6 +260,13 @@ type ChatStreamedResponse =
         chain_ids: number[];
         networks: NebulaContext["networks"];
       };
+    }
+  | {
+      event: "error";
+      data: {
+        code: number;
+        errorMessage: string;
+      };
     };
 
 type ChatStreamedEvent =
@@ -269,4 +294,8 @@ type ChatStreamedEvent =
   | {
       event: "context";
       data: string;
+    }
+  | {
+      event: "error";
+      data: string;
     };

apps/dashboard/src/app/nebula-app/(app)/components/ChatPageContent.tsx

@@ -578,6 +578,20 @@ export async function handleNebulaPrompt(params: {
           });
           return;
         }
+
+        case "error": {
+          hasReceivedResponse = true;
+          setMessages((prev) => {
+            return [
+              ...prev,
+              {
+                text: res.data.errorMessage,
+                type: "error",
+              },
+            ];
+          });
+          return;
+        }
       }
     },
     context: contextFilters,