Visible links, live physics, and exploring the graph

Three notes sent while brief 22 was being built: every link in the source visible and toggleable from the pane itself, one toggle set driving both panes, physics applied as the slider moves, and the explore workflow — focus on a selection, grow it degree by degree towards the peaks, with stats that price the next hop before you pay for it. Answers two of brief 22's questions; three remain open.