What a series is truncated against: the observation’s own ceiling, the amplitude a
dropped tail provably stays within, and the floor a tail no bound sums falls under.
A collapse decided for one extent and not yet run: each row of_spectral_sum_or_point and
render would take, run over that extent or over its nonzero part.
How a Body::Node reaches a value at one instant, and how many components it holds: a
closed form on its own holds no node, so the caller holding the graph answers both.
FORMAT 6.2 truncates a series once, at collapse: every term the ceiling and the precision
leave becomes an ordinary atom before the first sample is read.