docs(portal-self-service): frontend-decisions + demo note for S-08a (refs #65)

Record the workspace/tooling decisions (pnpm, Nx scoped to apps/+libs/, Vitest,
no @nx/docker, no Nx Cloud, Gitea-only) and a demo note for running the placeholder
app. NL DS deferred to S-08c.

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

docs/frontend-decisions.md

@@ -0,0 +1,31 @@
+# Frontend decisions
+
+A running log of frontend tooling and component decisions (CLAUDE.md §10). One entry per
+decision; record *why*, and note any deviation from NL Design System.
+
+---
+
+## Workspace & tooling (S-08a, #65)
+
+The portals live in an **Nx monorepo at the repository root**, alongside the .NET `services/`.
+
+- **Package manager: pnpm.** Native build scripts are approved explicitly in `pnpm-workspace.yaml`
+  under `allowBuilds` (pnpm 11 fails the install otherwise). Node 24, pnpm 11.
+- **Angular, standalone components + signals, no NgModules** (§10). Apps are generated with
+  `@nx/angular:application`.
+- **Unit tests: Vitest** via Angular's built-in `@angular/build:unit-test` (the `vitest-angular`
+  runner). **Angular Testing Library** is added for component tests when the first real components
+  land (S-08c); the S-08a placeholder uses a plain `TestBed` render assertion.
+- **Lint: ESLint** (flat config, `@nx/eslint`).
+- **Nx is scoped to `apps/` + `libs/` only.** The `@nx/docker` and `@nx/dotnet` plugins are **not**
+  installed — the .NET services are built by `dotnet`/the Makefile, and `@nx/docker` would otherwise
+  infer every `services/*/Dockerfile` as an unnamed Nx project and break the project graph.
+- **No Nx Cloud.** `nxCloudId` is stripped from `nx.json`; remote caching would depend on an
+  external service, and the repo is Gitea-only (§8.7). Nx's "configure-ai-agents" additions
+  (`.claude/settings.json`, a CLAUDE.md section referencing a GitHub marketplace) are **not**
+  committed for the same reason.
+- **CI:** a `frontend` job (`make frontend` → `pnpm install --frozen-lockfile` + `nx run-many -t
+  lint test build`) runs on pnpm + Node, with pinned action URLs (§15).
+
+**NL Design System:** not yet introduced — the S-08a app is a placeholder. NL DS components arrive
+with the submit form (S-08c, #67); any deviation from NL DS will be recorded here.