What is the current behavior?

On React Native / Expo, the auth accessToken callback reads from async storage (e.g. expo-secure-store). When subscribe() is called before the token has resolved, the phx_join payload is captured with no access_token. The stale join message is buffered, and when _onConnOpen() fires it flushes the buffer — sending the token-less join to the server.

The server accepts the join but cannot evaluate RLS policies without a token, so postgres_changes events are silently filtered out. The channel appears subscribed but no data arrives.

On browsers this never happens because localStorage.getItem() is synchronous, so the token is always available when subscribe() snapshots the join payload.

Fixes #1461
Related: #1477, #1725

What is the new behavior?

In _onConnOpen(), after the auth promise resolves:

1. Patch each channel's joinPush payload with the now-available accessTokenValue
2. Clear stale buffered join messages (they captured the old token-less payload in a closure)
3. Re-send the join for channels still in joining state

On browsers this is a no-op — the token was already present at subscribe() time.