Update .gitignore to exclude TypeScript build info and add dist directory. Expand README with project overview, technology stack, prerequisites, and instructions for running and testing the application.

src/HSchool.Server/Net/GameClient.cs

@@ -0,0 +1,58 @@
+using System.Net.WebSockets;
+using System.Threading.Channels;
+
+namespace HSchool.Server.Net;
+
+/// <summary>
+/// One connected browser. Frames are queued instead of written inline so a slow client
+/// can never stall the game loop; when the outbox overflows the oldest snapshot is dropped,
+/// which is exactly what you want for state that is resent 20 times a second.
+/// </summary>
+internal sealed class GameClient(uint playerId, WebSocket socket)
+{
+    private const int OutboxCapacity = 32;
+
+    private readonly Channel<ReadOnlyMemory<byte>> _outbox =
+        Channel.CreateBounded<ReadOnlyMemory<byte>>(new BoundedChannelOptions(OutboxCapacity)
+        {
+            FullMode = BoundedChannelFullMode.DropOldest,
+            SingleReader = true,
+            SingleWriter = false,
+        });
+
+    private bool _ready;
+
+    public uint PlayerId { get; } = playerId;
+
+    public WebSocket Socket { get; } = socket;
+
+    public string Name { get; set; } = $"player-{playerId}";
+
+    /// <summary>
+    /// Set once the welcome frame is out. Snapshots are only queued for ready clients, so a
+    /// connection never sees world state before it knows its own entity id.
+    /// </summary>
+    public bool IsReady => Volatile.Read(ref _ready);
+
+    public void MarkReady() => Volatile.Write(ref _ready, true);
+
+    /// <summary>Queues a frame. Returns false once the connection is shutting down.</summary>
+    public bool TrySend(ReadOnlyMemory<byte> frame) => _outbox.Writer.TryWrite(frame);
+
+    /// <summary>Pumps queued frames to the socket until cancelled or the outbox completes.</summary>
+    public async Task RunSendLoopAsync(CancellationToken cancellationToken)
+    {
+        await foreach (var frame in _outbox.Reader.ReadAllAsync(cancellationToken).ConfigureAwait(false))
+        {
+            if (Socket.State != WebSocketState.Open)
+            {
+                break;
+            }
+
+            await Socket.SendAsync(frame, WebSocketMessageType.Binary, endOfMessage: true, cancellationToken)
+                .ConfigureAwait(false);
+        }
+    }
+
+    public void CompleteOutbox() => _outbox.Writer.TryComplete();
+}