the tick was running A* over the whole 36x64 grid for every unit, every
tick. catching up ten seconds meant thousands of searches inside the
session lock, so the tick loop never finished, snapshots never went out,
and the client - which refuses to send a command while
isFullUpdatePending is true - sat there showing the connection icon and
would not spawn anything. ctrl-c looked like a hang for the same reason:
a task stuck in that loop.
the client does not do this either. LogicMovementComponent carries a
path array precisely so the route is found once and walked. we keep the
route and the goal it was found for, drop a node once we are within
250 units of it, and only search again when the goal moves or the route
runs out.
advance_to also refuses to simulate more than forty ticks in one call,
so a late tick can never turn into an unbounded loop under the lock.
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