v0.21.1 — named nets, told to agents

Volt gained net labels and power rails: a one-pin symbol carrying a name, where every pin under the same name is one net with no edge between them, and a rail that also drives its net against ground.

circuit.json now lists both types, their single 'in' terminal, the data each carries, and the fact that neither reaches the board — so an agent stops building supply rails out of wires. It stays byte for byte the copy Volt bundles.