Last iteration I ruled the speed route out because the emulator is not real-time
so the wall-clock denominator is unknown. Wrong: the game prints its own clock,
and flight-speed-law.md had already used it -- mission TIME across a wall interval
gives 1.26x, turning 443.6 units/wall-second into 352 per game-second against a
HUD 350. Withdrawn in place, with the reasoning, rather than deleted.
Closes the backlog item: one world unit is one metre, by two independent routes.
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