agent: Encourage model to include displayed fields first (#29308)

Instructs the model to include the fields that we display first in the
input object, so that e.g the user can see the path of a file while the
model generates the content.

Release Notes:

- N/A

crates/assistant_tools/src/create_file_tool.rs

@@ -24,6 +24,9 @@ pub struct CreateFileToolInput {
     ///
     /// You can create a new file by providing a path of "directory1/new_file.txt"
     /// </example>
+    ///
+    /// Make sure to include this field before the `contents` field in the input object
+    /// so that we can display it immediately.
     pub path: String,
 
     /// The text contents of the file to create.