Timers never fire in --headless --exec mode (the game loop runs but
does not process the timer queue without explicit step() calls).
Replace the Timer-based screenshot with a step() loop that advances
the engine 30 ticks at 10ms each before calling automation.screenshot().
This fix was discovered and applied as part of blog post 0033 publication
(Kanboard #209 / #345).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
