Mission Run Overview
Mission Run: Doctrine Schema Diagrams and PlantUML Rendering
Give the doctrine artefacts code-grounded schema diagrams, add local PlantUML rendering to the docsite, and add per-module code-to-docs READMEs.
Scope B of the docs-plans/doctrine split. Adds local build-time PlantUML rendering to the DocFX docsite (own ADR, amends R-04/#1839, cites the existing plantuml-diagramming toolguide), authors @startyaml schema diagrams of the doctrine artefacts generated from the frozen code models with an automated drift guard, fills the genuinely-thin artefact kinds, and adds small pointer-only README.md files to the doctrine source modules so agents and maintainers reach the canonical docs in one hop. Makes the codebase legible for future review/spec work.