S00-003: Record blocked task and remediation handoff

Changes: Preserve incomplete work and blocker metadata for S00-003. This checkpoint does not mark implementation accepted.
Validation: Session ended with status blocked.
Blocker: Stanza 12.22.1 browser HMAC sha-512 fails RFC 4231 Test Case 1: wrong 64-byte block selection. SCRAM-SHA-512 derives that hyphenated algorithm; private algorithm mutation/vendor patches are unsupported. Parent cannot attest browser strongest-mechanism compatibility from Node-only success.

Task: S00-003
Agent: auto-protocol-dcdf92cd067e
Role: protocol
Action: claim
Status: blocked

Task title: Проверить XMPP WSS/auth библиотеку

state/issues/S00-003-auto-protocol-dcdf92cd067e.json

@@ -0,0 +1,32 @@
+{
+  "title": "Validate browser-compatible SCRAM-SHA-512 through a public mechanism API",
+  "reason": "Stanza 12.22.1 browser HMAC sha-512 fails RFC 4231 Test Case 1: wrong 64-byte block selection. SCRAM-SHA-512 derives that hyphenated algorithm; private algorithm mutation/vendor patches are unsupported. Parent cannot attest browser strongest-mechanism compatibility from Node-only success.",
+  "reproduction": "Run the inline diagnostic in state/evidence/S00-003-auto-protocol-dcdf92cd067e.md using accepted Node runtime; sha-512 mismatches fixed RFC/Node digest while sha512 alias and SHA-256/SHA-1 controls match. Source Hmac.js uses alg === sha512 for 128-byte blocks.",
+  "role": "crypto",
+  "reviewer_role": "security",
+  "scope": [
+    "experiments/0002-xmpp-library/sha512-validation/**",
+    "docs/decisions/0002-xmpp-sha512-validation.md"
+  ],
+  "outcome": "One isolated runnable independently reviewed browser-compatible SCRAM-SHA-512 integration uses vetted existing crypto through a supported public mechanism API and validates proof/server-final without vendor/private-field patching or custom primitives.",
+  "steps": [
+    "Read original blocker, accepted stack/SASL ADR and pinned browser implementation/public APIs.",
+    "Reproduce the HMAC alias defect and evaluate an existing vetted mechanism/backend or candidate with primary docs, exact pins, license and browser/API checks.",
+    "Implement only isolated SCRAM-SHA-512 integration via supported public APIs using existing cryptographic code; retain fail-closed mutual authentication and real absence of channel binding.",
+    "Run fixed known vectors and full exchange positive/negative checks against the browser-resolved backend; preserve evidence, limitations and handoff for independent security review."
+  ],
+  "acceptance": [
+    "RFC SHA-512 known vectors match using actual browser-compatible crypto backend, including algorithm spelling and varied key lengths.",
+    "Full SCRAM-SHA-512 client proof and verified server-final agree with an independent existing implementation/fixed externally derived vector; missing/forged/premature final fails without authentication/restart.",
+    "Integration uses public mechanism APIs, correct SCRAM-SHA-512 wire name, no private-field/vendor patch, invented binding, custom primitives or plaintext downgrade.",
+    "Runnable pinned fixture experiment and browser bundle/backend evidence permit independent review; no parent WSS/library selection/shared contract work."
+  ],
+  "checks": [
+    "Reproduce original browser sha-512 HMAC mismatch.",
+    "Fixed SHA-512/HMAC known vectors including long keys using selected browser backend.",
+    "Full SCRAM-SHA-512 verified exchange and forged/missing/out-of-order server-final rejection.",
+    "Exact dependency/license/API/browser checks and repeatable clean install/bundle plus focused suite."
+  ],
+  "depends_on": [],
+  "requires_user_input": false
+}