Adds the request shapes + response interfaces. POPUP_ONLY_TYPES set grows by three. SW handlers in service-worker/vault.ts land in the next tasks. The new union members would make popup-only.ts's exhaustive handle() switch non-total (TS2366), so a default case is added returning an explicit "unhandled popup message" error. create_vault/attach_vault get real cases in Tasks 3.2-3.3; get_vault_status in Dev-C's Phase 6. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>