correct thinking modes for each model

src/engine.rs

@@ -1690,12 +1690,13 @@ fn conversation_key(system: &str, reasoning: ReasoningMode, messages: &[ChatTurn
         output.extend_from_slice(value.as_bytes());
     }
 
-    let mut output = b"DS4Server chat checkpoint v4".to_vec();
+    let mut output = b"DS4Server chat checkpoint v5".to_vec();
     text(&mut output, system);
     output.push(match reasoning {
         ReasoningMode::Direct => 0,
-        ReasoningMode::High => 1,
-        ReasoningMode::Max => 2,
+        ReasoningMode::Low => 1,
+        ReasoningMode::High => 2,
+        ReasoningMode::Max => 3,
     });
     for message in messages {
         output.push(u8::from(message.user));