GAP-1: add 'fontWeight' to the text-node key list in resolveNodeForCanvas so
$type-*-weight refs resolve to a number before reaching the renderer.
GAP-2: replace the early-exit `if (!variables || Object.keys(variables).length === 0)
return node` with `if (!variables) variables = {}` so DEFAULT_PALETTE_FALLBACK
fires even when the document has an empty variables map (un-seeded v1 docs).
Adds 2 new tests to fallback-equivalence.test.ts covering both gaps.
dc656be409