Add tabbed help UI with enhanced navigation

- Refactor `render_help` to display tabbed UI for help topics.
- Introduce `help_tab_index` to manage selected tab state.
- Allow navigation between help tabs using Tab, h/l, and number keys (1-5).
- Enhance visual design of help sections using styled tabs and categorized content.
- Update input handling to reset tab state upon exit from help mode.

crates/owlen-tui/src/chat_app.rs

@@ -60,6 +60,7 @@ pub struct ChatApp {
     saved_sessions: Vec<SessionMeta>,   // Cached list of saved sessions
     selected_session_index: usize,      // Index of selected session in browser
     save_name_buffer: String,           // Buffer for entering save name
+    help_tab_index: usize,              // Currently selected help tab (0-4)
 }
 
 impl ChatApp {
@@ -108,6 +109,7 @@ impl ChatApp {
             saved_sessions: Vec::new(),
             selected_session_index: 0,
             save_name_buffer: String::new(),
+            help_tab_index: 0,
         };
 
         (app, session_rx)
@@ -232,6 +234,10 @@ impl ChatApp {
         self.selected_session_index
     }
 
+    pub fn help_tab_index(&self) -> usize {
+        self.help_tab_index
+    }
+
     pub fn cycle_focus_forward(&mut self) {
         self.focused_panel = match self.focused_panel {
             FocusedPanel::Chat => {
@@ -1041,7 +1047,7 @@ impl ChatApp {
                                     }
                                 }
                             }
-                            "load" | "open" => {
+                            "load" | "open" | "o" => {
                                 // Load saved sessions and enter browser mode
                                 match self.storage.list_sessions() {
                                     Ok(sessions) => {
@@ -1175,9 +1181,27 @@ impl ChatApp {
                     _ => {}
                 },
                 InputMode::Help => match key.code {
-                    KeyCode::Esc | KeyCode::Enter => {
+                    KeyCode::Esc | KeyCode::Enter | KeyCode::Char('q') => {
                         self.mode = InputMode::Normal;
+                        self.help_tab_index = 0; // Reset to first tab
                     }
+                    KeyCode::Tab | KeyCode::Right | KeyCode::Char('l') => {
+                        // Next tab
+                        if self.help_tab_index < 4 {
+                            self.help_tab_index += 1;
+                        }
+                    }
+                    KeyCode::BackTab | KeyCode::Left | KeyCode::Char('h') => {
+                        // Previous tab
+                        if self.help_tab_index > 0 {
+                            self.help_tab_index -= 1;
+                        }
+                    }
+                    KeyCode::Char('1') => self.help_tab_index = 0,
+                    KeyCode::Char('2') => self.help_tab_index = 1,
+                    KeyCode::Char('3') => self.help_tab_index = 2,
+                    KeyCode::Char('4') => self.help_tab_index = 3,
+                    KeyCode::Char('5') => self.help_tab_index = 4,
                     _ => {}
                 },
                 InputMode::SessionBrowser => match key.code {