feat(dx): WP-43 — plop generators (value-object, form-machine)

Runnable `npm run gen:value-object` / `gen:form-machine` (plop) that scaffold the two
pure-TS house patterns with a co-located spec: a branded value object + parseX (mirrors
postcode/bsn), and an Elm-style form/wizard machine (Draft/Valid/Errors + Editing/
Submitting/Submitted/Failed union + initial/pure reduce/assertNever). Prompts take
context + PascalCase name (positional-arg bypass); a post-action reminds to add the
English target for the generated $localize id. Templates in plop-templates/ (prettier-
ignored). Skills (value-object, form-machine) point at the generators. ui-component +
bff-endpoint stay skill-driven (Angular {{}} / backend + gen:api).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.prettierignore

@@ -15,5 +15,8 @@ src/app/showcase/snippets.generated.ts
 # Vendored design system (CIBG Huisstijl)
 public/cibg-huisstijl/
 
+# Plop generator templates (Handlebars, not valid TS)
+plop-templates/
+
 # Backend is formatted by `dotnet format`, not prettier
 backend/