[djl11]

Follows #28. Every hero so far drew the "IPC: SPEAK / NOTIFY / WAIT" arrow from the fast brain to the SteerableToolHandle bus, or left the fast brain unwired, when the IPC link runs between the fast brain and the slow brain. The vector hero it is drawn from routed that arrow through the bus's corner (fixed in unifyai/branding 3d39b21).

• hero-architecture-light.png and hero-architecture-dark.png are regenerated through the image-model path in branding's docs-diagrams pipeline, at the same size and file name. The IPC arrow now runs from the fast brain up into the slow brain, clear of the bus.
• Everything else is as in Put the diagrams' mark on solid ground and regenerate the hero #28: the flat mark on a solid ground, colour by role, and every label checked against the layout spec.