theme=system audit (D2 prerequisite): the schema accepts $spacing-*
expression refs in gap/padding, but both Rust layout paths zero them
out — jian-core container_to_style and op-pen-loader gap_value fall
through Expression to 0 — so a ref collapses the layout instead of
resolving. Exactly three emission sites existed: modal_shell's card
padding ($spacing-5) and gap ($spacing-3), and toast's pill gap
($spacing-2). Emit the palette-equal numbers (24/12/8) in every mode,
same pattern as the numeric font-size toast fix (011f4104). A new
catalog-wide invariant test builds all kinds with theme=system and
rejects any expression gap/padding, so future ports can't reintroduce
the class. Color $refs are unaffected — scene_vars resolves fill and
stroke refs at paint.
ebcb85a569