Joint smoothness and spatial periodicity for the actual T iterates.
The IsClassicalSol predicate already packages joint smoothness up to
the initial time and spatial periodicity. This module exposes those facts as
an iteration-indexed API, including the base iterate T 0 = θprev.
Every actual iterate through the budget is jointly smooth on the
closed nonnegative-time domain. For positive iterates this is the smoothness
field of IsClassicalSol; the base iterate uses the classical previous-scale
solution.
Every nonnegative-time slice of an actual T iterate is spatially smooth.
Spatial periodicity of every actual iterate through the finite iteration budget.
Joint regularity and periodicity of the terminal iterate used as
T_{m-1} in the Section 5 residuals.