Relay animations: brute-force offsets so no link carries two dots

For a looping network animation where dots relay agent to agent (next hop leaves when the previous arrives), model each relay as a closed walk padded with short handoff pauses to a shared loop length, so the speed stays exact and the loop seamless. Random start offsets let two relays share a link at once. Fix: precompute each relay's occupied (frame, undirected-edge) set and grid-search the other relays' offsets for zero intersection (90 steps squared runs in seconds); assert zero so a later tweak can't silently reintroduce clashes, then verify per frame with an independent counter.