refactor(lifetime): own render resource prefixes

Give terrain, sky, retained UI, portal preparation, and the update/render frame pair explicit single owners. Make shader, texture, text, bindless, and GL construction prefixes checked and retryable so partial failure cannot lose or replay resource ownership.

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

src/AcDream.App/Rendering/RestoredTextureBindingMutation.cs

@@ -0,0 +1,83 @@
+using System.Runtime.ExceptionServices;
+
+namespace AcDream.App.Rendering;
+
+/// <summary>
+/// Runs a texture mutation with the caller's prior binding restored on every
+/// exit path. The concrete GL adapter supplies checked commands; tests can
+/// fault each edge without requiring a graphics context.
+/// </summary>
+internal sealed class RestoredTextureBindingMutation
+{
+    private uint? _pendingRestore;
+    private bool _operationActive;
+
+    internal bool HasPendingRestore => _pendingRestore.HasValue;
+
+    public void Execute(
+        Func<uint> readBinding,
+        Action<uint> bind,
+        uint mutationBinding,
+        Action mutation)
+    {
+        ArgumentNullException.ThrowIfNull(readBinding);
+        ArgumentNullException.ThrowIfNull(bind);
+        ArgumentNullException.ThrowIfNull(mutation);
+        if (_operationActive)
+            throw new InvalidOperationException("A texture-binding mutation is already active.");
+
+        _operationActive = true;
+        try
+        {
+            ExecuteCore(readBinding, bind, mutationBinding, mutation);
+        }
+        finally
+        {
+            _operationActive = false;
+        }
+    }
+
+    private void ExecuteCore(
+        Func<uint> readBinding,
+        Action<uint> bind,
+        uint mutationBinding,
+        Action mutation)
+    {
+        if (_pendingRestore is uint pending)
+        {
+            bind(pending);
+            _pendingRestore = null;
+        }
+
+        uint previousBinding = readBinding();
+        _pendingRestore = previousBinding;
+        Exception? mutationFailure = null;
+        try
+        {
+            bind(mutationBinding);
+            mutation();
+        }
+        catch (Exception failure)
+        {
+            mutationFailure = failure;
+        }
+
+        try
+        {
+            bind(previousBinding);
+            _pendingRestore = null;
+        }
+        catch (Exception restoreFailure)
+        {
+            if (mutationFailure is not null)
+                throw new AggregateException(
+                    "Texture mutation and binding restoration both failed.",
+                    mutationFailure,
+                    restoreFailure);
+            throw;
+        }
+
+        if (mutationFailure is not null)
+            ExceptionDispatchInfo.Capture(mutationFailure).Throw();
+    }
+}