Bind Reddit and Matrix session identities

tests/browser-client.test.ts

@@ -36,10 +36,10 @@ describe('BrowserClient', () => {
     expect(JSON.stringify(logger)).not.toContain('secret');
   });
 
-  it('reads the username from Reddit\'s nested me.json account response', async () => {
+  it('reads the username and stable account ID from Reddit\'s nested me.json response', async () => {
     const fetchMock = vi.fn().mockResolvedValue({
       ok: true,
-      json: async () => ({ kind: 't2', data: { name: 'bot-account' } }),
+      json: async () => ({ kind: 't2', data: { name: 'bot-account', id: 'abc123' } }),
     });
     vi.stubGlobal('fetch', fetchMock);
     const page = {
@@ -50,6 +50,10 @@ describe('BrowserClient', () => {
     const client = new BrowserClient(getTestConfig(), createLogger(), runtime);
 
     await expect(client.getAuthenticatedUsername()).resolves.toBe('bot-account');
+    await expect(client.getAuthenticatedIdentity()).resolves.toEqual({
+      username: 'bot-account',
+      accountId: 't2_abc123',
+    });
     expect(fetchMock).toHaveBeenCalledWith(
       'https://www.reddit.com/api/me.json',
       { credentials: 'include' },