fix: correctly forward error payload to launchdarkly (#285)

## Summary

Ensure that the SDK correctly reports the error payload to LaunchDarkly.

## How did you test this change?

<img width="2209" height="1922" alt="image"
src="https://github.com/user-attachments/assets/cb6977b3-b891-4f9a-a505-ed865d0338ec"
/>

## Are there any deployment considerations?

no

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Parses/merges error payload into span attributes and forwards it to
LaunchDarkly error events; sets default error source to "frontend".
> 
> - **Observe SDK (`sdk/observe.ts`)**:
> - Merge JSON from `errorMsg.payload` into error span attributes and
forward integrations a stringified `payload`.
>   - Set default error `source` to `"frontend"` in `recordError`.
> - **LaunchDarkly Integration (`integrations/launchdarkly/index.ts`)**:
> - Parse `error.payload` and include its fields in `LD_ERROR_EVENT`
tracking payload.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
e33ef4f. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: Vadman97

sdk/highlight-run/src/integrations/launchdarkly/index.ts

@@ -246,9 +246,17 @@ export class LaunchDarklyIntegrationSDK implements IntegrationClient {
 	}
 
 	error(sessionSecureID: string, error: ErrorMessage) {
+		let payload: { [key: string]: string } = {}
+		try {
+			if (error.payload) {
+				payload = JSON.parse(error.payload)
+			}
+		} catch (e) {}
+		const { payload: _, ...errorWithoutPayload } = error
 		this.client.track(LD_ERROR_EVENT, {
-			...error,
+			...errorWithoutPayload,
 			sessionID: sessionSecureID,
+			...payload,
 		})
 	}
 

sdk/highlight-run/src/sdk/observe.ts

@@ -221,6 +221,14 @@ export class ObserveSDK implements Observe {
 		errorMsg: ErrorMessage,
 		payload?: { [key: string]: string },
 	) {
+		try {
+			if (errorMsg.payload) {
+				payload = {
+					...JSON.parse(errorMsg.payload),
+					...(payload ? payload : {}),
+				}
+			}
+		} catch (e) {}
 		this.startSpan('highlight.exception', (span) => {
 			// This is handled in the callsites, but this redundancy handles it from a pure
 			// type safety perspective.
@@ -237,8 +245,12 @@ export class ObserveSDK implements Observe {
 				...payload,
 			})
 		})
+		const { payload: _, ...errorWithoutPayload } = errorMsg
 		for (const integration of this._integrations) {
-			integration.error(getPersistentSessionSecureID(), errorMsg)
+			integration.error(getPersistentSessionSecureID(), {
+				...errorWithoutPayload,
+				payload: JSON.stringify(payload),
+			})
 		}
 	}
 
@@ -266,7 +278,7 @@ export class ObserveSDK implements Observe {
 			event,
 			type: type ?? 'custom',
 			url: window.location.href,
-			source: source ?? '',
+			source: source ?? 'frontend',
 			lineNumber: res[0]?.lineNumber ? res[0]?.lineNumber : 0,
 			columnNumber: res[0]?.columnNumber ? res[0]?.columnNumber : 0,
 			stackTrace: res,