Step 2 (code quality): dedup + stop FE recomputing a server rule

- H1: tasksFromProfile takes the server's eligibleForHerregistratie decision
  instead of recomputing isHerregistratieEligible — the FE renders the rule,
  doesn't own it (ADR-0001). Policy reference impl kept for tests.
- M1: one shared runSubmit(fn, fallback) wrapper; the 4 submit-* commands keep
  only their payload mapping. +spec.
- M2: whenTag() kernel helper removes 10 repeated `as Extract<U,{tag}>` casts
  across the wizard/form components.

M4 (shared JA_NEE) folded into the upcoming i18n pass (clean dedup needs
$localize labels to sit in shared without breaking the English-shared-UI rule).
L1 already resolved by the restyle commit.

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

src/app/shared/application/submit.ts

@@ -0,0 +1,20 @@
+import { Result, ok, err } from '@shared/kernel/fp';
+import { problemDetail } from '@shared/infrastructure/api-error';
+
+/**
+ * Run a mutating API call and fold it into a `Result` — the one place the
+ * try/catch + ProblemDetails-mapping lives, so every `submit-*` command is just
+ * its own payload mapping. The backend re-validates and returns a 422
+ * ProblemDetails on rejection, surfaced here as the error string.
+ */
+export async function runSubmit<T>(fn: () => Promise<T>, fallback: string): Promise<Result<string, T>> {
+  try {
+    return ok(await fn());
+  } catch (e) {
+    return err(problemDetail(e, fallback));
+  }
+}
+
+// ponytail: i18n in Step 3/M3 wraps this in $localize with a stable @@id, which
+// dedupes it at the translation layer; for now it's the single shared default.
+export const SUBMIT_FAILED = 'Het indienen is niet gelukt. Probeer het later opnieuw.';