- Cull connections whose thin middle would render below ~0.8px
(MIN_WMID); drop external source/exit nodes whose connectors are
all culled, while site page nodes always stay
- Bead simulation persists across data reloads: emitters keyed per edge
direction, beads tracked by progress, so unrelated count changes no
longer reshuffle bead positions
- Bead speed relative to span length: constant 1.5s traversal per edge
- Top lane labeled with a house icon; all lane labels left-aligned just
past the source pill (half height on near-vertical branch lanes), with
guides running to the lane end so long slugs are never truncated