Root cause of 'two users can't chat': all accounts on one browser shared a
single IndexedDB, so the second registration overwrote the first's Signal
identity keys, corrupting both. Verified via two-isolated-client integration
test (real crypto.js + store.js) that the protocol itself is correct.
- store.js: useAccount(username) namespaces IndexedDB as cipher:<username>;
keys generated at registration now persist under the right account
- accounts.js: localStorage-backed account registry + active pointer
- app.js: multi-account boot/activate, account-switch/add/logout menu,
error toasts on send/decrypt failures (no more silent failures)
- login guards against missing on-device keys (multi-device linking still TODO)
- SW cache v2->v3 + precache accounts.js
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
