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/blockers/S00-019.md

@@ -0,0 +1,22 @@
+# Blocker S00-019
+
+- Original task: S00-003
+- Root task: S00-003
+- Reporter: auto-protocol-dcdf92cd067e
+- Role: protocol
+- Original owner: auto-protocol-dcdf92cd067e
+- Waits for user/external condition: False
+
+## Cause
+
+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.
+
+## One remediation 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.
+
+## Evidence / 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.
+
+The reporting agent must stop now. A new agent implements only S00-019.