Harden multiplayer room startup and defaults

[agustin-lowpoly]

Summary

• default multiplayer room creation to E1M7 when available
• prevent presence messages before multiplayer hello is accepted
• preserve pending hello authority while trusted gameplay definitions load
• correct remote player model facing without changing gameplay/hit logic

Validation

• node test/multiplayer/protocol.test.mjs
• pnpm build
• node test/browser/runMultiplayerBrowserSmoke.mjs --map e1m7 --duration-ms 3000 --json-out bench/results/quake/multiplayer-browser-smoke-e1m7.json
• local DOM check confirmed multiplayer menu selects E1M7 The House of Chthon by default
• node bench/captureMultiplayerPlayerCloseup.mjs
• node bench/captureMultiplayerCombatProof.mjs