refactor(app): compose session and player startup

Move streaming, live-session, hydration, local-player, combat, and teleport construction behind the typed Phase-7 boundary. Add exact-owner runtime bindings and focused spawn-claim classification so partial startup rolls back without retaining old session targets while preserving the accepted construction and frame dependencies.

Co-authored-by: Codex <codex@openai.com>

src/AcDream.App/Streaming/DatSpawnClaimHydrationClassifier.cs

@@ -0,0 +1,57 @@
+using AcDream.Content;
+using DatReaderWriter.DBObjs;
+
+namespace AcDream.App.Streaming;
+
+/// <summary>
+/// Memoized range check for indoor spawn claims. Claims below the indoor-cell
+/// range are always hydratable; indoor claims are validated against the exact
+/// landblock's authored cell count.
+/// </summary>
+internal sealed class DatSpawnClaimHydrationClassifier
+{
+    private readonly Func<uint, LandBlockInfo?> _lookup;
+    private (uint Claim, bool Unhydratable)? _memo;
+
+    public DatSpawnClaimHydrationClassifier(
+        IDatReaderWriter dats,
+        object datLock)
+        : this(CreateLookup(dats, datLock))
+    {
+    }
+
+    internal DatSpawnClaimHydrationClassifier(
+        Func<uint, LandBlockInfo?> lookup) =>
+        _lookup = lookup ?? throw new ArgumentNullException(nameof(lookup));
+
+    public bool IsUnhydratable(uint claim)
+    {
+        uint low = claim & 0xFFFFu;
+        if (low < 0x0100u)
+            return false;
+        if (_memo is { } memo && memo.Claim == claim)
+            return memo.Unhydratable;
+
+        LandBlockInfo? info = _lookup((claim & 0xFFFF0000u) | 0xFFFEu);
+        bool unhydratable = info is null
+            || info.NumCells == 0
+            || low >= 0x0100u + info.NumCells;
+        _memo = (claim, unhydratable);
+        return unhydratable;
+    }
+
+    public void Reset() => _memo = null;
+
+    private static Func<uint, LandBlockInfo?> CreateLookup(
+        IDatReaderWriter dats,
+        object datLock)
+    {
+        ArgumentNullException.ThrowIfNull(dats);
+        ArgumentNullException.ThrowIfNull(datLock);
+        return id =>
+        {
+            lock (datLock)
+                return dats.Get<LandBlockInfo>(id);
+        };
+    }
+}

src/AcDream.App/Streaming/LocalPlayerTeleportController.cs

@@ -41,6 +41,17 @@ internal sealed class DeferredLocalPlayerTeleportNetworkSink
             throw new InvalidOperationException("The local teleport sink is already bound.");
     }
 
+    public IDisposable BindOwned(ILocalPlayerTeleportNetworkSink inner)
+    {
+        Bind(inner);
+        return new Binding(this, inner);
+    }
+
+    private void Unbind(ILocalPlayerTeleportNetworkSink expected)
+    {
+        _ = Interlocked.CompareExchange(ref _inner, null, expected);
+    }
+
     public void OnTeleportStarted(uint sequence) => Required().OnTeleportStarted(sequence);
 
     public void OfferDestination(
@@ -53,6 +64,23 @@ internal sealed class DeferredLocalPlayerTeleportNetworkSink
     private ILocalPlayerTeleportNetworkSink Required() =>
         _inner ?? throw new InvalidOperationException(
             "The local teleport sink was used before composition completed.");
+
+    private sealed class Binding : IDisposable
+    {
+        private DeferredLocalPlayerTeleportNetworkSink? _owner;
+        private readonly ILocalPlayerTeleportNetworkSink _expected;
+
+        public Binding(
+            DeferredLocalPlayerTeleportNetworkSink owner,
+            ILocalPlayerTeleportNetworkSink expected)
+        {
+            _owner = owner;
+            _expected = expected;
+        }
+
+        public void Dispose() =>
+            Interlocked.Exchange(ref _owner, null)?.Unbind(_expected);
+    }
 }
 
 internal interface ILocalPlayerTeleportInputLifetime