fix: System message handling in chat service

Ensures the system message is updated if the configured
system message changes. Adds logging to clarify when
the system message is being updated or skipped.

Author: allozaur

tools/server/webui/src/lib/services/chat.ts

@@ -608,11 +608,23 @@ export class ChatService {
 
 		// If no system message is configured, return messages as-is
 		if (!systemMessage) {
+			console.log('No system message configured, returning original messages');
 			return messages;
 		}
 
 		// Check if first message is already a system message
 		if (messages.length > 0 && messages[0].role === 'system') {
+			// If the existing system message doesn't match current config, replace it
+			if (messages[0].content !== systemMessage) {
+				console.log('System message changed, replacing existing one');
+				const updatedMessages = [...messages];
+				updatedMessages[0] = {
+					role: 'system',
+					content: systemMessage
+				};
+				return updatedMessages;
+			}
+			
 			return messages;
 		}