fix action player wait actions to properly delay playback finish

Wait actions now extend the minimum finish time based on their
timestamp + duration, ensuring timers and other async operations
have time to complete before playback ends and screenshot is taken.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

designer/src/testing/action_player.h

@@ -59,6 +59,7 @@ private:
     std::chrono::steady_clock::time_point m_start_time;
     std::chrono::steady_clock::time_point m_pause_time;
     int64_t m_paused_duration_ms = 0;
+    int64_t m_min_finish_time_ms = 0;  // Extended by wait actions
 
     ScreenshotCallback m_screenshot_cb;
     NavigateCallback m_navigate_cb;