Support long-running agent turns

src/engine/tokenizer.rs

@@ -196,6 +196,7 @@ impl Tokenizer {
             &[ChatTurn {
                 user: true,
                 tool: false,
+                system: false,
                 skip_previous_eos: false,
                 reasoning: None,
                 reasoning_complete: true,
@@ -255,6 +256,13 @@ impl Tokenizer {
             output.extend(self.tokenize_rendered(system_prompt));
         }
         for (index, message) in messages.iter().enumerate() {
+            if message.system {
+                if self.family == ModelFamily::Glm {
+                    output.push(self.system);
+                }
+                output.extend(self.tokenize_rendered(&message.content));
+                continue;
+            }
             if message.tool {
                 if self.family == ModelFamily::Glm {
                     output.push(self.observation);