feat: create common test helpers to reduce duplication across test modules

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/tests/modes/list_tests.rs

@@ -1,20 +1,16 @@
 #[cfg(test)]
 mod tests {
-    use tempfile::TempDir;
+    use crate::tests::common::test_helpers::{create_temp_dir, test_temp_dir_setup};
 
     #[test]
     fn test_list_mode_basic_setup() {
-        // Create a temporary directory for testing
-        let temp_dir = TempDir::new().expect("Failed to create temp directory");
-        
-        // Test that we can work with temporary directories
-        assert!(temp_dir.path().exists());
+        test_temp_dir_setup();
     }
 
     #[test]
     fn test_list_mode_directory_operations() {
         // Create a temporary directory for testing
-        let temp_dir = TempDir::new().expect("Failed to create temp directory");
+        let temp_dir = create_temp_dir();
         
         // Test reading directory contents (should be empty)
         let entries: Vec<_> = std::fs::read_dir(temp_dir.path())