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);
+        };
+    }
+}