Let built-in chat participants share metadata (#284636)

So we can find the response ID in order to restore Turns
Fix #272987

Author: roblourens

src/vs/workbench/api/common/extHostChatAgents2.ts

@@ -721,7 +721,7 @@ export class ExtHostChatAgents2 extends Disposable implements ExtHostChatAgentsS
 
 		for (const h of context.history) {
 			const ehResult = typeConvert.ChatAgentResult.to(h.result);
-			const result: vscode.ChatResult = agentId === h.request.agentId ?
+			const result: vscode.ChatResult = agentId === h.request.agentId || (isBuiltinParticipant(h.request.agentId) && isBuiltinParticipant(agentId)) ?
 				ehResult :
 				{ ...ehResult, metadata: undefined };
 
@@ -1122,3 +1122,7 @@ function raceCancellationWithTimeout<T>(cancelWait: number, promise: Promise<T>,
 		promise.then(resolve, reject).finally(() => ref.dispose());
 	});
 }
+
+function isBuiltinParticipant(agentId: string): boolean {
+	return agentId.startsWith('github.copilot');
+}