Add Nano Banana 2 artistic render of skills ecosystem diagram

Generated via the art skill (claude-art-skill / Nano Banana 2) using
Gemini 3.1 Flash Image at 2K 16:9. Radial hub-and-spoke layout with
RuVector database at centre, 14 colour-coded category clusters, 78
skill nodes, and 18 MCP server connections on dark navy background.

Complements the mermaid technical diagram at skills-ecosystem.mmd.

Co-Authored-By: claude-flow <ruv@ruv.net>

Author: Roo Code