feat: Implement lesson generation feature and update status display

- Added functionality to generate lessons based on code reviews, including prompts and instructions for the reviewer.
- Updated the `.gitignore` to exclude lesson documentation files.
- Removed the `/lesson` command from the help menu and command parsing.
- Enhanced the status bar to display a message when a lesson is being generated.
- Introduced a new `lesson_running` state to track lesson generation progress.
- Updated various components to handle the new lesson generation workflow, including subagent events and token usage tracking.

src/controller/command.rs

@@ -6,7 +6,6 @@
 pub enum Command {
     Help,
     Quit,
-    LessonInteractive,
     McpOpen,
     Clear,
     ClearConfirm,
@@ -49,7 +48,6 @@ pub fn parse_command(text: &str) -> Command {
         "/quit" => Command::Quit,
         "/clear" if arg1.is_empty() => Command::ClearConfirm,
         "/clear" => Command::Clear,
-        "/lesson" => Command::LessonInteractive,
         "/login" if arg1.is_empty() => Command::Login { provider: String::new() },
         "/login" if !arg1.is_empty() => Command::Login { provider: arg1.to_string() },
         "/edit" if !arg1.is_empty() => Command::Edit(arg1.to_string()),