ARROW_LINES and ARROW_EQUILATERAL stroke caps were accepted by the schema
and round-tripped from .fig files, but the renderer mapped every cap to
Butt, so imported arrows lost their heads and arrows could not be drawn
locally.
Add a pure arrow-cap geometry module to scene-graph (open-endpoint
collection with per-vertex cap overrides, weight-scaled head geometry)
and draw heads in the stroke color for LINE nodes and open VECTOR
centerline strokes, including the dashed-centerline path. Fold the head
reach into strokeOverflow and the node picture margin so heads are not
cropped by visual bounds, caches, or culling. Round-trip per-vertex
stroke caps through the .fig vector style override table so one-ended
Figma arrows import correctly. Expose both caps in the stroke inspector
cap picker with localized labels, and cover the renderer with an
arrow-stroke-caps Playwright canvas snapshot.
Claude-Session: https://claude.ai/code/session_012zjEbyLSBYyPpJP4fu1XNB
