Replace the tall portrait README ingestion SVG with two landscape
diagrams — "1 · Ingestion" (build the context layer) and "2 · Serving"
(agents query it through MCP) — wired in as transparent 2x PNGs that
read on GitHub light and dark.
Add docs-site/diagram-studio: a static React Flow page with custom
themed nodes and the inlined ktx mascot that renders both diagrams and
exports them to PNG via html-to-image (the diagrams' reproducible
source). Remove the superseded ingestion-flow SVGs.
