Escape markdown in tools' ui_text (#27502)

Escape markdown in tools' `ui_text`

<img width="628" alt="Screenshot 2025-03-26 at 10 43 23 AM"
src="https://github.com/user-attachments/assets/bb694821-aae7-4ccf-a35a-a3317b0222d5"
/>


Release Notes:

- N/A

crates/assistant_tools/src/find_replace_file_tool.rs

@@ -33,10 +33,10 @@ pub struct FindReplaceFileToolInput {
     /// </example>
     pub path: PathBuf,
 
-    /// A user-friendly description of what's being replaced. This will be shown in the UI.
+    /// A user-friendly markdown description of what's being replaced. This will be shown in the UI.
     ///
     /// <example>Fix API endpoint URLs</example>
-    /// <example>Update copyright year</example>
+    /// <example>Update copyright year in `page_footer`</example>
     pub display_description: String,
 
     /// The unique string to find in the file. This string cannot be empty;