fix(rendering): bound portal resource lifetime

Separate logical ownership, render publication, and GPU retirement across live entities, landblocks, particles, textures, mesh arenas, portal/UI teardown, and per-frame scratch storage. Add bounded DAT/texture caches, upload budgets, three-frame fence retirement, exact-incarnation appearance reconciliation, frame pacing, and extensive lifetime conformance coverage.\n\nThe seven-destination connected route now cuts peak working/private memory roughly in half, returns Caul to 125-153 FPS locally, and produces no WER or AMD reset.\n\nCo-authored-by: OpenAI Codex <codex@openai.com>

src/AcDream.App/Rendering/Wb/TextureAtlasSlotAllocator.cs

@@ -0,0 +1,55 @@
+namespace AcDream.App.Rendering.Wb;
+
+/// <summary>
+/// Owns the physical layer slots in one texture array. A released texture
+/// remains rented until the GPU-retirement callback returns its layer, so
+/// <see cref="AvailableCount"/> never advertises a CPU-unreferenced layer
+/// that an in-flight draw may still sample.
+/// </summary>
+internal sealed class TextureAtlasSlotAllocator
+{
+    private readonly bool[] _rented;
+    private readonly Stack<int> _returned = new();
+    private int _next;
+
+    public TextureAtlasSlotAllocator(int capacity)
+    {
+        ArgumentOutOfRangeException.ThrowIfLessThan(capacity, 1);
+        _rented = new bool[capacity];
+    }
+
+    public int AvailableCount => _returned.Count + (_rented.Length - _next);
+
+    public int Rent()
+    {
+        int slot;
+        if (_returned.Count != 0)
+        {
+            slot = _returned.Pop();
+        }
+        else
+        {
+            if (_next == _rented.Length)
+                throw new InvalidOperationException(
+                    $"Texture atlas has no GPU-safe layer available ({_rented.Length} layers)."
+                );
+            slot = _next++;
+        }
+
+        if (_rented[slot])
+            throw new InvalidOperationException($"Texture atlas layer {slot} was rented twice.");
+        _rented[slot] = true;
+        return slot;
+    }
+
+    public void Return(int slot)
+    {
+        ArgumentOutOfRangeException.ThrowIfNegative(slot);
+        ArgumentOutOfRangeException.ThrowIfGreaterThanOrEqual(slot, _next);
+        if (!_rented[slot])
+            throw new InvalidOperationException($"Texture atlas layer {slot} was returned twice.");
+
+        _rented[slot] = false;
+        _returned.Push(slot);
+    }
+}