S00-019: Validate browser SCRAM-SHA-512 through public mechanism composition

Changes: Add an isolated pinned mechanism wrapper using Stanza's public constructor and factory APIs, preserve the SCRAM-SHA-512 wire name and fail-closed final guard, and document the proposed ADR, browser bundle evidence, independent Scramp vectors, notices and limits. Leave parent selection, dependency experiments, specs and shared contracts unchanged.
Validation: Fresh-cache npm ci and Vite browser build pass; 87 focused tests pass, including RFC HMAC vectors, original defect reproduction, independent full SHA-512 exchanges and rejected invalid finals/order/reset paths. Hashed Scramp oracle fixture comparison passes. Dependency check verifies 49 locked entries, 25 installed pins/licenses and 340 unmodified Stanza files. make check passes 72 tooling tests. Native browsers, WSS/live server interoperability and production readiness are untested; independent security review remains pending.

Task: S00-019
Agent: auto-crypto-c68801170fa4
Role: crypto
Action: claim
Status: review

Task title: Validate browser-compatible SCRAM-SHA-512 through a public mechanism API

planning/TASK_MATRIX.md

@@ -1,6 +1,6 @@
 # Матрица задач
 
-Generated; state revision **48**. Canonical status: state/tasks.json.
+Generated; state revision **50**. Canonical status: state/tasks.json.
 
 | ID | Этап | Оператор | Reviewer | Статус | Owner | Зависимости | Задача |
 | --- | --- | --- | --- | --- | --- | --- | --- |
@@ -21,7 +21,7 @@ Generated; state revision **48**. Canonical status: state/tasks.json.
 | [S00-016](tasks/S00-016.md) | S00 | ci-cd | qa | done | auto-ci-cd-351a0cbbabef | S00-001, S00-011, S00-013, S00-014 | Restore reviewer model availability after provider capacity failure |
 | [S00-017](tasks/S00-017.md) | S00 | protocol | security | done | auto-protocol-599343cd9e3f | S00-001, S00-002 | Establish fail-closed SCRAM server-final validation |
 | [S00-018](tasks/S00-018.md) | S00 | protocol | security | done | auto-protocol-89fe6563092c | S00-001, S00-002, S00-017 | Validate bounded standalone XML ingress for the XMPP candidate |
-| [S00-019](tasks/S00-019.md) | S00 | crypto | security | todo |  | S00-001, S00-002, S00-017, S00-018 | Validate browser-compatible SCRAM-SHA-512 through a public mechanism API |
+| [S00-019](tasks/S00-019.md) | S00 | crypto | security | review | auto-crypto-c68801170fa4 | S00-001, S00-002, S00-017, S00-018 | Validate browser-compatible SCRAM-SHA-512 through a public mechanism API |
 | [S00-010](tasks/S00-010.md) | S00 | qa | orchestrator | todo |  | S00-001, S00-002, S00-003, S00-004, S00-005, S00-006, S00-007, S00-008, S00-009 | Gate: Профиль и проверка стека |
 | [S01-001](tasks/S01-001.md) | S01 | orchestrator | security | todo |  | S00-010 | Описать identity/model contracts |
 | [S01-002](tasks/S01-002.md) | S01 | orchestrator | security | todo |  | S00-010, S01-001 | Описать async account context |