openup: architecture notebook + EA diagram renders

- analysis-design/architecture-notebook.md: Architecture Notebook work
  product in the keyfob docx template structure (10 sections), grounded
  in mapping / design note / supplementary specs; embeds the component
  model and all 12 realization figures
- scripts/openup/export-diagram-images.ps1: read-only EA COM renderer
  (EA-15 findings: image API on ProjectInterface, OpenDiagram before
  export or blank stub, type 0 = PNG); renders reflect manual layouts
- renders: requirements/use-case-overview.png, analysis-design/
  uc-01..12-realization.png + component-architecture.png; embedded as
  figures in use-case-model.md and uc-realization-mapping.md
- BUILD-CHECKLIST 6.4 documents the exporter

docs/openup/model/BUILD-CHECKLIST.md

@@ -240,3 +240,12 @@ would destroy manual layout). Sources: `uc-realization-mapping.md` §2a (interac
    associations; Requirements tree untouched.
 4. Manual layout preserved: the scripts add no/modify no DiagramObjects in existing
    diagrams (only the new `Design` diagram carries its own object layout).
+
+### 6.4 Diagram image export — `scripts/openup/export-diagram-images.ps1`
+
+Read-only on the model: renders 14 diagrams to PNG for the markdown documents
+(`requirements/use-case-overview.png`, `analysis-design/uc-01..uc-12-realization.png`,
+`analysis-design/component-architecture.png`). EA-15 findings baked into the script:
+image methods live on **ProjectInterface** (not Repository); `PutDiagramImageToFile(id,
+path, 0)` = PNG; the diagram must be `OpenDiagram`-ed first or a blank 241×151 stub is
+written. Regenerate after model changes; renders reflect the manual layout.