docs(skills): extract house recipes as Claude Code skills for SSP templating

8 template-generic skills in .claude/skills/ (new-feature, new-context,
value-object, form-machine, bff-endpoint, mutation-command, ui-component,
new-ssp), condensed from CLAUDE.md/ARCHITECTURE/fp-tea/ADRs and pointing at
this repo's worked examples. CLAUDE.md gains a pointer.

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

.claude/skills/value-object/SKILL.md

@@ -0,0 +1,55 @@
+---
+name: value-object
+description: Add a validated input type (postcode, email, hours, id number, …) as a branded value object with a parser — "parse, don't validate". Use whenever a form field or API value has format rules.
+---
+
+# Value object (parse, don't validate)
+
+Raw input becomes a branded type only via a parser returning `Result`. Once you hold
+the type, never re-check it. Never model validity as a boolean flag next to a string.
+
+## Skeleton
+
+`<context>/domain/value-objects/<name>.ts` (pure TS, no Angular):
+
+```ts
+import { Brand, Result, ok, err } from '@shared/kernel/fp';
+
+export type Postcode = Brand<string, 'Postcode'>;
+
+export function parsePostcode(raw: string): Result<string, Postcode> {
+  const t = raw.trim().toUpperCase();
+  if (!/^[1-9]\d{3}\s?[A-Z]{2}$/.test(t)) {
+    return err($localize`:@@validation.postcode:Voer een geldige postcode in, bijv. 1234 AB.`);
+  }
+  // The parser also normalises — callers always hold the canonical form.
+  return ok(t.replace(/^(\d{4})\s?([A-Z]{2})$/, '$1 $2') as Postcode);
+}
+```
+
+Rules:
+- The `as Brand` cast appears **only** inside the parser — the type is mintable nowhere else.
+- Error message is user-facing → `$localize` with a stable `@@validation.<name>` id.
+- Trim/normalise before testing; return the cleaned value.
+- This is **format** feedback only. The server re-validates as authority (ADR-0001) — never encode business rules (existence, eligibility) here.
+
+## Spec (required)
+
+Co-located `<name>.spec.ts`: happy path, normalisation, each rejection case. Call the
+parser directly — no TestBed.
+
+## Wiring into a form
+
+The machine's `validate(draft)` calls the parsers and collects errors into
+`StepErrors`; the `Valid` type holds the branded values (see **form-machine** skill).
+
+## Worked examples
+
+`src/app/registratie/domain/value-objects/` — `postcode.ts`, `email.ts`, `uren.ts`,
+`big-nummer.ts`, each with a co-located spec.
+
+## Verify
+
+```bash
+npm test && npm run lint
+```