Tier 1 hardening: no more silent hangs, no writes before consent

Reliability, which is where most of these reach users:
- The worker RPC had no message validation, no error/messageerror
  listener, no timeout, and terminate() left every pending promise
  unsettled. A malformed frame threw inside the listener (posting no
  response at all) and a dead worker stranded its callers -- the
  documented innerHTML-remount hazard manifested as a permanent freeze
  rather than an error. Both sides now validate the envelope, calls
  time out at 60s, and worker death rejects everything outstanding.
- requestNwcConnection fired no pending event, so a host using the
  RECOMMENDED hidden-mount pattern navigated a hidden element to a
  consent screen nobody could see and waited forever. Now symmetric
  with bitlogin-offer-pending.

Consent integrity:
- vaultOfferCheck published an origin rebinding to relays -- a durable
  mutation of the user's account -- from a plain host API call before
  any consent screen existed. It is read-only now, and a wallet stored
  under a DIFFERENT origin no longer reports as already-saved, so the
  binding can only change through the consented path.
- offerNwcConnection's guard sat above three awaits; two concurrent
  calls both passed it and the second dropped the first's promise. The
  slot is claimed synchronously.

Vault reads fail closed:
- listConnections threw rather than returning a relay-shaped subset
  when quorum is not met -- a short listing is indistinguishable from
  "you have no connections", and one relay should not get to say that.
- The 500-record page limit is reported (truncated) instead of silently
  deciding which connections exist.

Supply chain:
- All eight crypto dependencies pinned to exact versions (they held
  users' keys behind caret ranges), and Bitcoin Connect with them.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01CMr9Yt8SYmZcfgrg3CV2G1

packages/widget/package.json

@@ -13,7 +13,7 @@
   },
   "dependencies": {
     "@bitlogin/core": "*",
-    "@getalby/bitcoin-connect": "^3.12.3"
+    "@getalby/bitcoin-connect": "3.12.3"
   },
   "devDependencies": {
     "typescript": "^5.7.3",