Add playlist support with marking and folder playback

- Mark files with 't' key (shown with * prefix in yellow)
- Clear marks with 'c' key
- Enter plays: marked files > whole folder > single file
- Navigate playlist with 'n' (next) and 'p' (previous)
- Show playlist position in status (e.g., "song.mp3 [3/10]")
- Collect all files recursively when playing folder
- Remove emoji icons from status panel
- Update help text with new keybindings

src/main.rs

@@ -113,14 +113,28 @@ async fn handle_key_event(state: &mut AppState, key_code: KeyCode) -> Result<()>
         KeyCode::Char('l') => {
             state.expand_selected();
         }
+        KeyCode::Char('t') => {
+            state.toggle_mark();
+        }
+        KeyCode::Char('c') => {
+            state.clear_marks();
+        }
+        KeyCode::Char('n') => {
+            state.play_next();
+            if let Some(ref path) = state.current_file {
+                tracing::info!("Next track: {:?}", path);
+            }
+        }
+        KeyCode::Char('p') => {
+            state.play_previous();
+            if let Some(ref path) = state.current_file {
+                tracing::info!("Previous track: {:?}", path);
+            }
+        }
         KeyCode::Enter => {
-            if let Some(item) = state.get_selected_item() {
-                if !item.node.is_dir {
-                    let path = item.node.path.clone();
-                    state.current_file = Some(path.clone());
-                    state.player_state = PlayerState::Playing;
-                    tracing::info!("Playing: {:?}", path);
-                }
+            state.play_selection();
+            if let Some(ref path) = state.current_file {
+                tracing::info!("Playing: {:?} (playlist: {} tracks)", path, state.playlist.len());
             }
         }
         KeyCode::Char(' ') => {