kv-wasm: onboarding (setup codes, enrollment tickets, scan-to-join) for the web vault

Mirrors kv-ffi's docs/10 §5 API in WebCore and binds it under the names the web app codes
against: setupPayloadForKit, addDevicePayload, revokeEnrollmentTicket, loginWithSetup,
joinStart/joinPoll/joinCancel, joinApprove, joinSend, and the free function parseSetupPayload
(also callable through the worker client).

Unlike kv-ffi, the Secret Key is not persisted: every unlock on the web takes it, so it is
kept zeroized in the unlocked state and dropped on lock. loginWithSetup refuses a code for a
different server than the configured origin (the browser only talks to its own origin).

Tests: ticket enrollment and scan-to-join in both roles against kv-ffi via the kv-sync test
server, a swapped-approver rejection, a Chrome test (IndexedDB never holds the Secret Key,
JS shapes, error codes) and a Node smoke check of the built package.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/kv-wasm/js/client.d.ts

@@ -6,6 +6,7 @@ import type {
   totpCode,
   matchUrl,
   coreVersion,
+  parseSetupPayload,
 } from "./kv_wasm.js";
 
 export * from "./kv_wasm.js";
@@ -22,6 +23,7 @@ export type RemoteVault = CoreMethods & {
   totpCode: Async<typeof totpCode>;
   matchUrl: Async<typeof matchUrl>;
   coreVersion: Async<typeof coreVersion>;
+  parseSetupPayload: Async<typeof parseSetupPayload>;
   /** Frees the core (zeroizing keys), releases the tab lock and terminates the worker. */
   close(): Promise<void>;
 };