docs(portal-openbaar): record openbaar decisions + walking-skeleton public-visibility demo (refs #10)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/frontend-decisions.md

@@ -103,3 +103,17 @@ with the submit form (S-08c, #67); any deviation from NL DS will be recorded her
   touching the app or its production config.
 - `tests/e2e` is a standalone Playwright project (its own `package.json`), not an Nx project — it's a
   live-stack check like the other `verify-*` runners, not part of the `frontend` unit lane.
+
+## Openbaar Register portal (S-09, #10)
+
+- **Anonymous, no auth.** The openbaar register is a public read, so `apps/openbaar` has no
+  `angular-auth-oidc-client`, no interceptor, and no `config.json` — `main.ts` bootstraps `appConfig`
+  directly with just `provideHttpClient` + `provideRouter`. This is the deliberate contrast to
+  self-service and keeps the app trivially cacheable/CDN-able.
+- **Same-origin via nginx, like self-service.** The compose `openbaar` image serves the built app and
+  reverse-proxies `/openbaar` to the BFF; the api-client's relative calls stay same-origin (no CORS).
+  Served on `:8141`, health-checked over IPv4 (`127.0.0.1`), no Keycloak dependency.
+- **Public-safe by construction.** The portal only ever sees the BFF's `OpenbaarProjection.PublicView`
+  (id + status); `bsn`/`naam` never leave the BFF. The e2e asserts the bsn never renders.
+- **Loads on open, filters on search.** `RegisterPage` fetches the full register on construction and
+  re-queries `/openbaar/register?q=` on search — no client-side filtering, the BFF owns the query.