Per docs/vision-edge-glyph.md: a `follows` edge (the derivation backbone)
draws two parallel shaft tails offset along the edge normal by a fixed
SCREEN-space gap (FOLLOWS_GAP_RATIO x edgeWidth — constant on screen at
every zoom, like the stroke width), converging on the shared single
arrowhead; `supports` keeps the plain single line (dashed was rejected
earlier — not revisited).
- CanvasEdge carries the edge type; graph-view passes it from the snapshot.
- followsEdgeGeometry (pure, tested): offset tails + convergence at the
head base — a strictly-parallel pair would poke out beside the head
whenever the screen-fixed gap exceeds the head's world-scaled base
half-width. The offset tails sit farther from the source center than
the axis start, so the source disc never clips them.
- Edge paths leave buildGeometry: their gap is anchored to the CURRENT
camera scale, so buildEdgePaths(k) rebuilds on geoVersion changes and
camera-scale drift (> EDGE_PATHS_ZOOM_EPSILON) — 0.08ms per rebuild at
211 edges; pans and settle frames reuse the cached paths.
- Legend entry bottom-right: ⟹ follows · → supports.
Live-verified: isolated follows edge (search "likelihood") shows two 1px
shafts with a ~3px centerline gap converging into one 8px-base shared
head; gap measured constant on screen at 0.2x, 1x, and 5x fit zoom while
heads/nodes scale. Gates: tsc, 435/435 tests, lint, build.
amosblomqvist
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