refactor(runtime): extract local teleport and player mode

Move local teleport, player-mode, animation, shadow, and sealed-dungeon lifetimes out of GameWindow. Make player-mode entry transactional and isolate approach completions by controller lifetime and approach generation so stale callbacks cannot affect replacements.

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

src/AcDream.App/Streaming/SealedDungeonCellClassifier.cs

@@ -0,0 +1,44 @@
+using DatReaderWriter;
+using DatReaderWriter.DBObjs;
+using DatReaderWriter.Enums;
+using AcDream.Content;
+
+namespace AcDream.App.Streaming;
+
+internal interface ISealedDungeonCellClassifier
+{
+    bool IsSealedDungeon(uint cellId);
+}
+
+/// <summary>
+/// Classifies a server-supplied full cell ID using the EnvCell's retail
+/// <see cref="EnvCellFlags.SeenOutside"/> bit. Missing, outdoor, and structural
+/// shell IDs are never guessed to be sealed.
+/// </summary>
+internal sealed class DatSealedDungeonCellClassifier
+    : ISealedDungeonCellClassifier
+{
+    private readonly IDatReaderWriter _dats;
+    private readonly object _datLock;
+
+    public DatSealedDungeonCellClassifier(
+        IDatReaderWriter dats,
+        object datLock)
+    {
+        _dats = dats ?? throw new ArgumentNullException(nameof(dats));
+        _datLock = datLock ?? throw new ArgumentNullException(nameof(datLock));
+    }
+
+    public bool IsSealedDungeon(uint cellId)
+    {
+        uint low = cellId & 0xFFFFu;
+        if (low < 0x0100u || low >= 0xFFFEu)
+            return false;
+
+        EnvCell? envCell;
+        lock (_datLock)
+            envCell = _dats.Get<EnvCell>(cellId);
+        return envCell is not null
+            && !envCell.Flags.HasFlag(EnvCellFlags.SeenOutside);
+    }
+}