Introduce IInterrupt marker interface, IInterruptHandlerCommand for
resolving
interrupts, and InterruptStore. When a pending interrupt exists at the
start
of a tick, system execution is skipped until resolved. Only one
interrupt of
a given type may be pending at a time.
Replace the empty placeholder design.md with comprehensive
design-basegame.md
and design-factions.md detailing game rules, setup, and mechanics for
the
card game 魔烬纷争.