Index into LoadPatternTable.
Index into SequenceSpec::stages: this load is only registered on
the Domain when that stage starts, not at decode time. This
matters whenever an earlier stage's LoadControl shares one
pseudo-time with every unfrozen pattern (core/src/analysis/
integrator.rs) — a pattern's reference load must not exist yet if
an earlier stage isn't meant to ramp it too (the same reason
core/tests/elements/force_beam.rs's native two-phase test adds its
lateral pattern's load only between phases, not upfront).
Index into
NodeTable.