Function PluginNode

Renders one plugin node on the canvas.

Handle layout encodes the port model:

• in (left, target) — omitted on listener, the pipeline entry point.
• success (right, source) — omitted on client, the terminal node; centered on listener, otherwise paired with the error handle.
• error (right, source, lower) — only on regular plugin nodes, i.e. neither listener nor client.

Clicking the node invokes data.onSelect(id); selection is shown with an accent border and ring.