fix: realm+microsoft auth race that crashes mineflayer plugin injection

[DallasCarraher]

Summary

• Realm auth (realmAuthenticate -> authenticate) is async, so onReady() — which wires up registerChannel/pluginChannels among other things — can still be pending when createClient() returns. mineflayer's plugin loader checks client.wait_connect immediately after createClient() returns and, if it's falsy, injects plugins right away instead of waiting for connect_allowed. That races ahead of onReady() and crashes every realm+microsoft consumer with bot._client.registerChannel is not a function before the device-code prompt even appears.
• wait_connect already exists for exactly this kind of gating (see autoVersion.js), it just wasn't set on the realm auth path. This sets it before the async chain starts and emits connect_allowed once onReady() has actually run.
• Also includes an earlier, related commit from this branch (surfacing setup errors via client.emit('error', ...) instead of letting them become an unhandled rejection) since it's what made this race visible/debuggable in the first place rather than failing silently.

Test plan

• Live-tested against a real Realm connection (Microsoft auth, realms.pickRealm) — previously crashed synchronously on bot._client.registerChannel is not a function before any device-code prompt; now connects and proceeds into the configuration handshake normally.
• No existing test in this repo's suite exercises the realm+microsoft path directly (it requires live Microsoft/Realms auth), so this is verified via live connection rather than an added unit test.