refactor(shared): delete unwrapOk, the unadopted test value-object helper (RB-33)

unwrapOk had zero consumers in apps/ or libs/ since ADR-0006 shipped it.
The one call site the finding named already satisfies the ADR's real
rule (call the real parser, never a cast) with an inline guard, so
adding a manufactured first caller was not the better fix. This commit
deletes the helper and its file, and updates the one doc sentence that
named it. The finding's call site is unchanged. See rb-33.md for the
full adopt-or-delete reasoning.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

libs/shared/src/testing/value-object.ts

@@ -1,14 +0,0 @@
-import { Result } from '@shared/kernel/fp';
-
-/**
- * Unwrap a `Result` produced by a REAL `parse*` value-object parser, throwing
- * if it isn't `ok`. This is the only sanctioned way for a spec to obtain a
- * branded value-object type — it closes off the `'garbage' as Postcode` cast
- * route, since the only door to the branded type is the parser itself.
- */
-export function unwrapOk<E, T>(result: Result<E, T>): T {
-  if (!result.ok) {
-    throw new Error(`unwrapOk: expected ok, got error: ${JSON.stringify(result.error)}`);
-  }
-  return result.value;
-}