Migrate Reliability Kroki diagrams to Themed SVG

Why

The earlier Themed SVG migration covered hand Mermaid figures (for example the rename-breakage mockup). Build-time Kroki PlantUML blocks and one inline Mermaid listing on Internet Reliability pages still published as fixed-color <img> assets, so they stayed light when the site toggle switched to dark mode.

Change

  • Converted Reference reliability’s PlantUML sequence to Mermaid source label-as-wire-break with adaptive + host Themed SVG outputs.

  • Converted Identity stack’s inline Mermaid and PlantUML planes figures to identity-stack-flowchart and identity-stack-planes.

  • Converted NDN and friends' PlantUML figure to ndn-delivery-vs-app-labels.

  • Registered the four stems in the diagram build/validate/render-test scripts; greenfield builds now preserve a true fixed Mermaid original from the pre-adapter render.

  • AsciiDoc pages use [.themed-svg] image blocks so the hub runtime can inline the host SVG under the manual theme toggle.