feat: gallery + generic blueprint viewer, add Grid blueprint

Refactor the List-specific screen into a data-driven, reusable viewer:
- generic Blueprint type + shared LoadState machine + registry
- vue-router: / (gallery) and /b/:slug (illustration)
- BlueprintViewer renders any blueprint; specimens stay bespoke
- add Grid blueprint (6 functions incl. Position) + GridSpecimen

README.md

@@ -11,6 +11,15 @@ The first screen illustrates the **List** blueprint and its seven functions —
 Display · Scroll · Load · Filter · Sort · Select · Act — as a specimen-under-glass with a
 full contract readout, an anatomy/composition map, and the `LoadState` machine.
 
+<!-- docs:start -->
+
+## Documentation
+
+- [CONTEXT.md](CONTEXT.md) — ubiquitous language (Blueprint, Viewer, Specimen, Readout, …)
+- [DESIGN.md](DESIGN.md) — architecture & build-out decisions
+
+<!-- docs:end -->
+
 ## Develop
 
 ```bash