- Add self-healing system for units with `selfHeal` definition (e.g. Commander)
- Healing pauses for 30 seconds after taking damage to prevent out-healing fights
- Rates converted to per-tick at load time for efficient simulation
- Improve build queue interaction: use CTRL (or Cmd) to chain multiple builds,
release to cancel placement automatically — no need to press Esc or click again
- Track queue modifier state from DOM events for robustness across focus loss
