fix(extension): binary-safe message transport + carrier-image guard

chrome.runtime.sendMessage serializes with a JSON-like algorithm that drops
ArrayBuffer/TypedArray payloads — they arrive as empty objects, so a carrier
JPEG reached the service worker as 0 bytes and failed with the opaque WASM
error "no SOF marker found in JPEG". This broke extension vault creation.

- shared/message-binary.ts: encodeBinary/decodeBinary deep-walk a message tree
  and base64-envelope every binary buffer so it survives the channel (chunked
  base64 to avoid stack overflow on multi-MB buffers); plain number[] untouched.
- Wire encode/decode at all four message boundaries: popup, service-worker
  onMessage listener (decode request, encode response), setup swSend, vault
  postToServiceWorker.
- handleCreateVault: magic-byte guard classifies empty / non-JPEG carriers into
  actionable errors (carrier_image_empty / carrier_image_not_jpeg) instead of
  the opaque WASM error; error-copy.ts adds user-facing text; setup errors now
  route through lookupErrorCopy.
- router SETUP_ALLOWED: add create_vault / attach_vault / generate_recovery_qr —
  the Phase-3 setup wizard sends these from the setup page and they were being
  rejected as unauthorized_sender.
- Tests: message-binary round-trip suite (7) + carrier-guard (2) + setup
  allowlist (3). 435/435 vitest, build:all clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pe8qw5KePDqAEBsAxnVQuJ

extension/src/service-worker/index.ts

@@ -4,6 +4,7 @@
 import type { Request, Response, SessionTimeoutConfig } from '../shared/messages';
 import type { RouterState } from './router/index';
 import { route } from './router/index';
+import { encodeBinary, decodeBinary } from '../shared/message-binary';
 import * as vault from './vault';
 import { clearCurrent } from './session';
 import * as sessionTimer from './session-timer';
@@ -74,7 +75,10 @@ chrome.commands.onCommand.addListener((command) => {
 });
 
 chrome.runtime.onMessage.addListener(
-  (request: Request, sender: chrome.runtime.MessageSender, sendResponse: (r: Response) => void) => {
+  (rawRequest: Request, sender: chrome.runtime.MessageSender, sendResponse: (r: Response) => void) => {
+    // Binary payloads (carrier/reference images, attachments, backups) cross
+    // the channel as base64 envelopes — decode before routing. See message-binary.ts.
+    const request = decodeBinary(rawRequest);
     (async () => {
       // Plan C Phase 5: invert the reset rule. Reset on every message
       // except a documented passive-read exclusion set, so an active
@@ -94,7 +98,8 @@ chrome.runtime.onMessage.addListener(
           // eslint-disable-next-line no-console
           console.warn(`[relicario sw] ${request.type} -> error:`, r.error);
         }
-        sendResponse(r);
+        // Re-encode binary in the response so it survives the channel back.
+        sendResponse(encodeBinary(r));
       })
       .catch((err: Error) => {
         // eslint-disable-next-line no-console