Load auth and server modules only when used

[u9g]

Problem

createClient.js requires the Microsoft auth dependency tree (prismarine-auth → @azure/msal-node → jsonwebtoken, plus xboxlive-auth and node-fetch) at module load for every consumer, though only auth: 'microsoft' clients ever call into it, and index.js loads createServer (node-rsa and the server plugins) for client-only consumers.

Profiled with a Module._load timing hook: this is ~70ms of the ~275ms first require('minecraft-protocol') on an M-series Mac with a cold-ish file cache (~10ms once the OS file cache is warm — msal-node is one large bundled file, so the win is concentrated where startup is already slowest). It also keeps a few MB of never-used code out of memory for offline bots.

Change

• createClient: require mojangAuth/microsoftAuth inside their switch branches, so they load on first authenticated connect.
• index.js: export createServer/Server through getters, so client-only consumers never load the server tree. Destructuring consumers (const { createServer } = require('minecraft-protocol')) still work — the getter fires at destructure time.

No behavior change for any auth mode; the modules load at the same points they were first used before.

Verification

standard clean; packet + cycle tests pass locally; offline-mode client connect exercised against a vanilla server via the mineflayer test suite.

[u9g]

Closing: re-measured on an idle machine the win is only ~10ms warm / ~65ms cold-cache — not worth the churn.