feat(fp): WP-09 — pure-logic closure: dates + missing command specs

Consolidate four hand-rolled nl-NL date formatters (tasks.ts, aanvraag-
block, letter-preview, aanvraag-view -- one more than the WP found) into
one shared/kernel/datum.ts::formatDatumNl, spec-pinned and empty-safe.
Add the two missing command specs CLAUDE.md's testing rule calls for:
draft-sync.spec.ts (debounce coalescing + trailing-call + submit Result
shape, via fake timers) and submit-change-request.spec.ts. Remove the
unused RemoteData.map3 (updating the three docs that mentioned it); the
variant input on confirmation.component.ts was already gone. Documents
both stale-WP-text corrections in the backlog file.

This closes out backlog Phase 1 (FP/DDD core, WP-05..09).

src/app/shared/application/remote-data.ts

@@ -71,20 +71,6 @@ export function map2<E, A, B, R>(
   return { tag: 'Success', value: f(a.value, b.value) };
 }
 
-/** Combine three sources (built on map2). */
-export function map3<E, A, B, C, R>(
-  a: RemoteData<E, A>,
-  b: RemoteData<E, B>,
-  c: RemoteData<E, C>,
-  f: (a: A, b: B, c: C) => R,
-): RemoteData<E, R> {
-  return map2(
-    map2(a, b, (x, y) => [x, y] as const),
-    c,
-    ([x, y], z) => f(x, y, z),
-  );
-}
-
 /** Chain a second source that depends on the first one's value. */
 export function andThen<E, A, B>(
   rd: RemoteData<E, A>,

src/app/shared/kernel/datum.spec.ts

@@ -0,0 +1,22 @@
+import { describe, it, expect } from 'vitest';
+import { formatDatumNl } from './datum';
+
+describe('formatDatumNl', () => {
+  it('formats a Date in long Dutch form', () => {
+    expect(formatDatumNl(new Date(2026, 6, 2))).toBe('2 juli 2026');
+  });
+
+  it('formats an ISO string the same way', () => {
+    expect(formatDatumNl('2026-07-02')).toBe('2 juli 2026');
+  });
+
+  it('is empty-safe: undefined, null, and empty string all yield the empty string', () => {
+    expect(formatDatumNl(undefined)).toBe('');
+    expect(formatDatumNl(null)).toBe('');
+    expect(formatDatumNl('')).toBe('');
+  });
+
+  it('returns empty for an unparseable string rather than "Invalid Date"', () => {
+    expect(formatDatumNl('not-a-date')).toBe('');
+  });
+});

src/app/shared/kernel/datum.ts

@@ -0,0 +1,16 @@
+/**
+ * The one hand-written date formatter for pure TS (non-template) code — a domain
+ * rule or a `$localize` string can't reach for Angular's `DatePipe`, so this covers
+ * that gap. Templates use `DatePipe` (`| date: 'longDate'`) instead; don't add a
+ * second hand-rolled formatter for either case.
+ */
+export function formatDatumNl(d: Date | string | undefined | null): string {
+  if (!d) return '';
+  const date = typeof d === 'string' ? new Date(d) : d;
+  if (Number.isNaN(date.getTime())) return '';
+  return new Intl.DateTimeFormat('nl-NL', {
+    day: 'numeric',
+    month: 'long',
+    year: 'numeric',
+  }).format(date);
+}