Guides dragged out of a ruler did not snap at all (only Shift to the ruler's
ticks): they now go through the engine (`Session::ruler_guide`, a
`NewGuide` previewing `guide.add`, one undo step) and snap as a moved guide
does: with Smart Guides to the edges, centres (so the sides' midpoints) and
anchors of the art and of the artboards, labelled; with Smart Guides off,
View > Snap to Point pulls new and moved guides onto anchors. Moving art
with the Selection tool already snapped flush to artboard edges and centres
with Smart Guides on; a test now covers it.
Artboard guides: `Guide.artboard` holds an artboard id (written only when
set, so canvas guides save as before and older files open unchanged).
`guide.add {artboard}` makes one, `guide.list` reports it; a guide dragged
out of a ruler with the Artboard tool belongs to the active artboard. It is
drawn, picked and snapped to across its artboard only, moves with it
(`artboard.move`, a pure move in `artboard.setProps`, `artboard.rearrange`),
is copied with it (`artboard.duplicate`, Alt-drag copy) and deleted with it
(`artboard.delete`, the guide selection kept in step).
Guides as Layers rows with their own lock and hide (part d) stay open: ruler
guides are not layer nodes; Lock Guides locks them all, and Make Guides
paths are Layers rows already. Listed in the ROADMAP parity row.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
5d65699043