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/app/state/misc.rs

@@ -79,7 +79,6 @@ const COMMANDS: &[&str] = &[
     "/help",
     "/quit",
     "/clear",
-    "/lesson",
     "/login",
     "/login zen",
     "/login openai",
@@ -291,6 +290,7 @@ pub struct MiscState {
     pub api_context_length: Option<u32>,
     pub tick_count: u64,
     pub todo_content: String,
+    pub lesson_running: bool,
 }
 
 impl MiscState {
@@ -309,6 +309,7 @@ impl MiscState {
             api_context_length: None,
             tick_count: 0,
             todo_content: String::new(),
+            lesson_running: false,
         }
     }