A node type can now say which outside thing its parameters point at, and
nodes sharing one — a broker topic, a URL, a bucket — are drawn as a single
neuron on a new /brain canvas. That makes the wiring which runs between
flows through a broker visible for the first time; no single flow's canvas
can show it. The key is read off stored parameters, so a credential
reference never reaches an id.
Layout is a d3 force simulation settled once and then frozen, lit by the
socket the editor already listens to: a neuron pulses when any node behind
it publishes, and its connections light as values pass.
Fixes the message pulse while here: interpolating the stroke against the
edge's `color-mix()` resting colour went through oklab and left the gamut,
which turned every pulse on both canvases fluorescent yellow.
stroblme
302d3b8af3