Multiplayer: networked dedicated server + desktop client over MrGameEng.Net

Engine bump brings MrGameEng.Net (WebSocket transport, RFC 6455 server,
delta component replication) — this commit is its showcase.

LittleSim.Server --listen runs the world online: 24 pawns wander, tire
and rest on the engine's fixed-tick HeadlessHost (the same Wander/
Needs/Decision systems the windowed world uses), a WebSocketServer
accepts clients and a ReplicationServer ships Transform2D + PawnNeeds
deltas at 10 snapshots/s per the shared NetSchema. --probe is the CLI
check: it connects, listens for a second and prints replicated pawns
with positions sampled twice to show the world is alive.

The game gains MultiplayerScene (dotnet run --project src/LittleSim --
--connect [ws://host:port]): simulation stays on the server, the client
applies snapshots into its scene store, decorates spawned entities with
sprites and reuses PawnAppearanceSystem so replicated fatigue darkens
pawns locally. HUD strings go through ru/en localization; the `net`
console command reports connection state and entity count. Esc returns
to the main menu.

Verified end to end: probe sees 24 pawns moving between samples; the
windowed client connects and runs against a live local server.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -31,6 +31,9 @@ git submodule update --init             # after fresh clone
 dotnet build LittleSim.sln
 dotnet run --project src/LittleSim -c Release   # measure perf in Release only
 dotnet run --project src/LittleSim.Server -- --days 10 --tps 60   # headless fast-forward
+dotnet run --project src/LittleSim.Server -- --listen             # multiplayer world (WebSocket)
+dotnet run --project src/LittleSim -- --connect                    # client → ws://localhost:9050
+dotnet run --project src/LittleSim.Server -- --probe               # CLI check of a running server
 dotnet test LittleSim.sln                        # runs the engine test suites
 ```