feat(server): update message preprocessing to handle tree structure

src/lib/server/endpoints/preprocessMessages.ts

@@ -9,7 +9,34 @@ export async function preprocessMessages(
 ): Promise<EndpointMessage[]> {
 	return Promise.resolve(messages)
 		.then((msgs) => downloadFiles(msgs, convId))
-		.then((msgs) => injectClipboardFiles(msgs));
+		.then((msgs) => injectClipboardFiles(msgs))
+		.then((msgs) => expandPersonaResponses(msgs));
+}
+
+/**
+ * Expand messages with personaResponses into the content field
+ * For multi-persona messages, concatenate all persona responses
+ * This ensures all personas see what others said in previous turns
+ */
+function expandPersonaResponses(messages: EndpointMessage[]): EndpointMessage[] {
+	return messages.map((message) => {
+		// If message has persona responses, format them into content
+		if (message.personaResponses && message.personaResponses.length > 0) {
+			const personaContents = message.personaResponses
+				.map((pr) => {
+					// Format: "[PersonaName]: content"
+					const name = pr.personaName || pr.personaId;
+					return `[${name}]: ${pr.content}`;
+				})
+				.join("\n\n");
+
+			return {
+				...message,
+				content: personaContents,
+			};
+		}
+		return message;
+	});
 }
 
 async function downloadFiles(messages: Message[], convId: ObjectId): Promise<EndpointMessage[]> {