S00-021: Record verified browser OMEMO backend blocker for S00-004

Changes:
- Re-ran both committed probes unchanged (smoke exit 0 SMOKE_PASS; wasm-unsupported exit 2 UNSUPPORTED_BLOCKER) and recorded actual outputs in state/evidence/S00-021-auto-crypto-fcef9b6781bf.md.
- Verified on the reachable npm proxy that no maintained browser/WASM-capable OMEMO2 package exists: @signalapp/libsignal-client 0.105.0 is native-only (zero .wasm); @signalapp/libsignal, omemo-client, omemo-top, omemo-wasm, @converse/omemo are all E404.
- Wrote docs/decisions/0003-crypto-library.md (proposed) documenting the verified audited session/ratchet + persistence capability and the honest blocker for the browser/worker/WASM endpoint and OMEMO2 wire layer, with traceable primary sources.
- Wrote state/handoffs/S00-021.md with the reproducible next step for the S00-004 continuation.

Validation:
- smoke.mjs -> exit 0 (SMOKE_PASS, 631-byte record byte-for-byte reload).
- wasm-unsupported.mjs -> exit 2 (wasmFiles 0, native prebuilds only).
- npm view E404s confirmed against the same proxy that returns @signalapp/libsignal-client 0.105.0, so responses are genuine.
- make check: 72 tooling tests passed (OK).
- No source changes outside scope: experiments/** unchanged; only state/tasks.json (workflow metadata) plus the in-scope ADR. S00-004 stays blocked (honest blocker), not bypassed.

Task: S00-021
Agent: auto-crypto-fcef9b6781bf
Role: crypto
Action: claim
Status: review

Task title: Устранить прерывание: Проверить browser OMEMO backend

state/tasks.json

@@ -1,6 +1,6 @@
 {
   "schema_version": 1,
-  "revision": 57,
+  "revision": 59,
   "tasks": {
     "S00-001": {
       "status": "done",
@@ -1279,10 +1279,14 @@
       "updated_at": "2026-10-15T07:27:20+00:00"
     },
     "S00-021": {
-      "status": "todo",
-      "owner": null,
+      "status": "review",
+      "owner": "auto-crypto-fcef9b6781bf",
       "external_wait": false,
-      "reason": null
+      "reason": null,
+      "started_at": "2026-10-15T08:32:48+00:00",
+      "updated_at": "2026-10-15T08:38:43+00:00",
+      "evidence": "state/evidence/S00-021-auto-crypto-fcef9b6781bf.md",
+      "handoff": "state/handoffs/S00-021.md"
     }
   },
   "events": [
@@ -2017,6 +2021,29 @@
       "from": "in_progress",
       "to": "blocked",
       "reason": "Agent timed out; process terminated before escalation"
+    },
+    {
+      "revision": 58,
+      "at": "2026-10-15T08:32:48+00:00",
+      "action": "claim",
+      "task": "S00-021",
+      "agent": "auto-crypto-fcef9b6781bf",
+      "role": "crypto",
+      "from": "todo",
+      "to": "in_progress",
+      "reason": null
+    },
+    {
+      "revision": 59,
+      "at": "2026-10-15T08:38:43+00:00",
+      "action": "submit",
+      "task": "S00-021",
+      "agent": "auto-crypto-fcef9b6781bf",
+      "role": null,
+      "from": "in_progress",
+      "to": "review",
+      "reason": null,
+      "evidence": "state/evidence/S00-021-auto-crypto-fcef9b6781bf.md"
     }
   ],
   "retired_agents": [