story-kit: merge 271_story_show_assigned_agent_in_expanded_work_item_view

Adds assigned agent display to the expanded work item detail panel.
Resolved conflicts by keeping master versions of bot.rs (permission
handling), ChatInput.tsx, and fs.rs. Removed duplicate list_project_files
endpoint and tests from io.rs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/http/io.rs

@@ -401,4 +401,5 @@ mod tests {
         let result = api.list_directory(payload).await;
         assert!(result.is_err());
     }
+
 }