Fix a bunch of other low-hanging style lints (#36498)

- **Fix a bunch of low hanging style lints like unnecessary-return**
- **Fix single worktree violation**
- **And the rest**

Release Notes:

- N/A

crates/acp_thread/src/acp_thread.rs

@@ -49,7 +49,7 @@ impl UserMessage {
         if self
             .checkpoint
             .as_ref()
-            .map_or(false, |checkpoint| checkpoint.show)
+            .is_some_and(|checkpoint| checkpoint.show)
         {
             writeln!(markdown, "## User (checkpoint)").unwrap();
         } else {

crates/acp_thread/src/mention.rs

@@ -79,12 +79,10 @@ impl MentionUri {
                     } else {
                         Ok(Self::Selection { path, line_range })
                     }
+                } else if input.ends_with("/") {
+                    Ok(Self::Directory { abs_path: path })
                 } else {
-                    if input.ends_with("/") {
-                        Ok(Self::Directory { abs_path: path })
-                    } else {
-                        Ok(Self::File { abs_path: path })
-                    }
+                    Ok(Self::File { abs_path: path })
                 }
             }
             "zed" => {