Verify Reddit identity before Matrix capture

tests/account-auth-context.test.ts

@@ -1,8 +1,22 @@
 import { describe, expect, it, vi } from 'vitest';
-import { AccountAuthContext } from '../src/services/account-auth-context.js';
+import {
+  AccountAuthContext,
+  authenticateCurrentAccount,
+} from '../src/services/account-auth-context.js';
 import { createMockLogger } from './mockLogger.js';
 
 describe('AccountAuthContext', () => {
+  it('does not attempt Matrix capture until Reddit identity is authoritative', async () => {
+    const refreshMatrixCredentials = vi.fn();
+
+    await expect(authenticateCurrentAccount({
+      getRedditUsername: vi.fn().mockResolvedValue(null),
+      refreshMatrixCredentials,
+    })).resolves.toBeNull();
+
+    expect(refreshMatrixCredentials).not.toHaveBeenCalled();
+  });
+
   it('fails closed until Reddit and Matrix resolve to one authenticated account', async () => {
     const auth = new AccountAuthContext(createMockLogger());
     const authenticate = vi.fn().mockResolvedValue({