docs: add repository-derived architecture and workflow diagrams #43

Parent

Part of #40.

What to build

Give contributors and users accurate architecture and workflow diagrams that are generated from maintained project facts and published with the public documentation.

Acceptance criteria

• Diagrams describe the actual implemented architecture and user workflow, not roadmap assumptions.
• Machine-readable sources capture the repository facts needed to generate the diagrams.
• Generated diagrams are committed SVG and render deterministically.
• Public documentation includes the diagrams with accessible text alternatives.
• task brand:check detects missing or stale generated diagrams, and CI reports drift.
• Diagram labels and related copy distinguish implemented behavior from planned work.
• Diagram labels and generated content contain no emoji characters.