Fix: System-wide type hardening and V3 API alignment

src/lib/ae_elements/AE_AITools.svelte

@@ -94,11 +94,11 @@
 
         try {
             ae_promises = ai_client.chat.completions.create({
-                model: model,
+                model: model || 'dgrzone-deepseek-8b-quick',
                 max_tokens: maxTokens,
                 temperature: temperature,
                 messages: [
-                    { role: 'system', content: systemPrompt },
+                    { role: 'system', content: systemPrompt || 'You are a helpful assistant.' },
                     { role: 'user', content: content }
                 ]
             }).then((resp) => {