S00-004: Record blocked task and remediation handoff

Changes: Preserve incomplete work and blocker metadata for S00-004. This checkpoint does not mark implementation accepted.
Validation: Session ended with status blocked.
Blocker: S00-004 acceptance requires establishing legacy/OMEMO2 AND worker/wasm AND persistence without a homegrown ratchet. Reproduced (this run) probes and live public-registry queries confirm only the audited session/ratchet engine + persistence are verified (@signalapp/libsignal-client@0.105.0, Node native addon, zero .wasm). The browser/worker/WASM deployment and the OMEMO/OMEMO2 wire layer are not available from any maintained package on the reachable registry (@signalapp/libsignal, @converse/omemo, @xmpp/omemo, omemo2, omemo-js, omemo-client, omemo-top, omemo-wasm all E404). ENC-009 forbids a homegrown algorithm/ratchet and ENC-011 forbids substituting media AES-GCM for the OMEMO2 wire format, so the spike cannot synthesize a browser backend inside S00-004 scope.

Task: S00-004
Agent: auto-crypto-fe1c81c17ded
Role: crypto
Action: claim
Status: blocked

Task title: Проверить browser OMEMO backend

planning/stages/S00.md

@@ -9,7 +9,7 @@
 - [S00-001](../tasks/S00-001.md): Утвердить Web-профиль — orchestrator; done.
 - [S00-002](../tasks/S00-002.md): Выбрать framework и build runtime — orchestrator; done.
 - [S00-003](../tasks/S00-003.md): Проверить XMPP WSS/auth библиотеку — protocol; blocked.
-- [S00-004](../tasks/S00-004.md): Проверить browser OMEMO backend — crypto; todo.
+- [S00-004](../tasks/S00-004.md): Проверить browser OMEMO backend — crypto; blocked.
 - [S00-005](../tasks/S00-005.md): Выбрать IndexedDB wrapper и migration policy — storage; todo.
 - [S00-006](../tasks/S00-006.md): Зафиксировать browser/reference matrix — orchestrator; todo.
 - [S00-007](../tasks/S00-007.md): Утвердить password и crypto unlock модель — security; todo.
@@ -26,6 +26,7 @@
 - [S00-019](../tasks/S00-019.md): Validate browser-compatible SCRAM-SHA-512 through a public mechanism API — crypto; done.
 - [S00-020](../tasks/S00-020.md): Restore access to the pinned Linux XMPP experiment toolchain — ci-cd; in_progress.
 - [S00-021](../tasks/S00-021.md): Устранить прерывание: Проверить browser OMEMO backend — crypto; done.
+- [S00-022](../tasks/S00-022.md): Confirm or source a verified browser/WASM-capable OMEMO2 backend for the Web client endpoint — crypto; blocked.
 - [S00-010](../tasks/S00-010.md): Gate: Профиль и проверка стека — qa; todo.
 
 ## Граница этапа