Fix bad cd sometimes used by BashTool and set edit model temperature to 0 (#26656)

Release Notes:

- N/A

crates/assistant_tools/src/edit_files_tool.rs

@@ -151,7 +151,7 @@ impl EditFilesTool {
                 messages,
                 tools: vec![],
                 stop: vec![],
-                temperature: None,
+                temperature: Some(0.0),
             };
 
             let mut parser = EditActionParser::new();