M1: add NGO + Multiplayer Services packages and prototype scripts (compiling)

Netcode for GameObjects 2.13.0 + Unity Multiplayer Services 2.2.4 (unified
Relay/Lobby SDK; supersedes deprecated standalone relay/lobby). Four M1
scripts, verified against live editor reflection and compiling clean:
- Net/NetworkBootstrap.cs  Relay host/join-by-code harness (IMGUI)
- Net/PlayerDriver.cs       replicated host-auth capsule (input->ServerRpc->host)
- Bot/TreadPart.cs          v0.1 tread feel: snap-to-cruise/lock-pivot/lean
- Bot/SeatManager.cs        left/right tread seat claim + leaver-safety

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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