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/tasks.json

@@ -324,7 +324,8 @@
       "depends_on": [
         "S00-001",
         "S00-002",
-        "S00-021"
+        "S00-021",
+        "S00-022"
       ],
       "requirements": [
         "ENC-003",
@@ -1223,6 +1224,61 @@
       ],
       "context_budget_chars": 48000
     },
+    {
+      "id": "S00-022",
+      "stage": "S00",
+      "kind": "blocker",
+      "root_task": "S00-004",
+      "blocker_depth": 1,
+      "unblocks": [
+        "S00-004"
+      ],
+      "role": "crypto",
+      "reviewer_role": "security",
+      "title": "Confirm or source a verified browser/WASM-capable OMEMO2 backend for the Web client endpoint",
+      "outcome": "One independently reviewed, traceable primary-source outcome that establishes a verified browser/worker/WASM-capable OMEMO2 backend (a maintained library with a real web/WASM build and an OMEMO2/S ce-format mapping, or an approved external library/provider decision with license + support + browser constraints), preserving the verified audited session/ratchet engine and persistence from the existing spike, without a homegrown ratchet or ENC-009/ENC-011 bypass.",
+      "depends_on": [
+        "S00-001",
+        "S00-002",
+        "S00-021"
+      ],
+      "requirements": [
+        "ENC-003",
+        "ENC-009",
+        "ENC-011"
+      ],
+      "scope": [
+        "docs/decisions/0003-crypto-library.md"
+      ],
+      "inputs": [
+        "docs/WEB_PROFILE.md",
+        "docs/ARCHITECTURE.md",
+        "docs/CONTRACTS.md",
+        "docs/TESTING.md",
+        "roles/crypto.md",
+        "docs/decisions/README.md",
+        "state/blockers/S00-022.md"
+      ],
+      "spec_sections": [],
+      "ui_sections": [],
+      "steps": [
+        "Read S00-004 blocker evidence, ADR 0003, and accepted ENC-003/ENC-009/ENC-011 with ADRs 0000-0002.",
+        "Confirm the residual browser/worker/WASM OMEMO2 backend is unavailable from any maintained package on the reachable registry (reproduce wasm-unsupported probe and npm view queries).",
+        "Source or confirm a maintained browser/worker/WASM-capable OMEMO2 encryption layer: verify its web/WASM build, license, primary-source docs, support, and an OMEMO2 wire mapping against ENC-011; or record the concrete external product/administrative decision (library, provider, or license acceptance) required to bring such a backend in.",
+        "Run a focused known-answer OMEMO2 roundtrip in the web-compatible target and record actual results (or record an unsupported format blocker, not success) and update docs/decisions/0003-crypto-library.md; submit evidence and handoff for independent security review."
+      ],
+      "acceptance": [
+        "A browser/worker/WASM-capable OMEMO2 backend is established with a real, verified web build and an OMEMO2 wire mapping from traceable primary sources, or an explicit external decision (with specific requested input) is recorded that unblocks sourcing it.",
+        "The OMEMO2 wire-format mapping does not bypass ENC-009/ENC-011 client-endpoint encryption.",
+        "No homegrown ratchet, no spec/plan/shared-contract change without plan, no secrets in evidence, and no out-of-scope edits; unsupported format recorded as blocker, not success."
+      ],
+      "checks": [
+        "Known-answer OMEMO2 roundtrip in the web/WASM target, or a traceable upstream/external decision covering ENC-009/ENC-011.",
+        "Web/WASM asset presence verified (non-zero real footprint), license and support checked.",
+        "Independent security review confirms no bypass and no unsupported format counted as success."
+      ],
+      "context_budget_chars": 48000
+    },
     {
       "id": "S00-010",
       "stage": "S00",