v0.31.0 — Transform engine facet decomposition

House-cleaning on the most central package in the project. transformRune in packages/transform/src/engine.ts resolves every universal rune axis — tint, density, width, spacing, reading, elevation, prominence, motion, background, frame, substrate, cover — in one ~800-line function whose steps are numbered 1, 1b, 1c … 1h, 2 … 9. This milestone replaces that section with a facet registry (SPEC-124): one module per axis, dependencies declared rather than implied by statement order, and a driver that merges their contributions.

No feature work. Every step is behaviour-preserving, and the governing rule is that the 630 pre-existing transform tests never change — they run through the public entry point, so an edit to accommodate a migration is a bug report, not a fix.