fix: Resolve build errors and warnings, and update grammar

Co-authored-by: aider (openai/andrew/openrouter/sonoma-sky-alpha) <aider@aider.chat>

src/modes/diff.rs

@@ -117,7 +117,7 @@ pub fn mode_diff(
 
     validate_diff_args(cmd, &ids, &tags)?;
 
-    let settings = crate::config::Settings::new(args, crate::config::default_dir()?)?;
+    let settings = crate::config::Settings::new(args, crate::config::Settings::default_dir()?)?;
 
     let item_service = crate::services::item_service::ItemService::new(settings.dir.clone());