Crosspost targets: one row when they fit, stacked otherwise

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app.rs

@@ -792,10 +792,11 @@ impl App {
             return;
         }
         match key.code {
-            KeyCode::Up | KeyCode::Char('k') => {
+            // Up/Down for the stacked layout, Left/Right for the single row.
+            KeyCode::Up | KeyCode::Left | KeyCode::Char('k' | 'h') => {
                 self.target_cursor = self.target_cursor.saturating_sub(1)
             }
-            KeyCode::Down | KeyCode::Char('j') => {
+            KeyCode::Down | KeyCode::Right | KeyCode::Char('j' | 'l') => {
                 self.target_cursor = (self.target_cursor + 1).min(n - 1)
             }
             KeyCode::Char(' ') | KeyCode::Enter => {