refactor(app): compose world rendering startup

Move Region/environment, mandatory modern rendering, terrain, WB, texture, and sampler construction behind the typed Phase-4 composition boundary. Give every fallible GL constructor prefix retryable ownership so partial startup failure cannot leak or replay resource deletion while preserving the accepted render path and DAT inputs.

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

src/AcDream.App/Rendering/ResourceCleanupGroup.cs

@@ -1,5 +1,7 @@
 namespace AcDream.App.Rendering;
 
+using System.Runtime.ExceptionServices;
+
 /// <summary>
 /// Reverse-order, all-attempted cleanup owner used while a composite resource
 /// is still under construction and after it becomes the aggregate owner.
@@ -25,6 +27,15 @@ internal sealed class ResourceCleanupGroup : IRetryableResourceCleanup
         _entries.Add(new Entry(name, release));
     }
 
+    public void TransferAll()
+    {
+        if (_running)
+            throw new InvalidOperationException(
+                "The resource cleanup group is currently releasing resources.");
+        foreach (Entry entry in _entries)
+            entry.Complete = true;
+    }
+
     public void RetryCleanup()
     {
         if (_running || IsCleanupComplete)
@@ -60,4 +71,26 @@ internal sealed class ResourceCleanupGroup : IRetryableResourceCleanup
         if (failures is not null)
             throw new AggregateException("Composite resource cleanup remains incomplete.", failures);
     }
+
+    public void RollbackConstructionAndThrow(
+        string message,
+        Exception constructionFailure)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(message);
+        ArgumentNullException.ThrowIfNull(constructionFailure);
+        try
+        {
+            RetryCleanup();
+        }
+        catch (Exception cleanupFailure)
+        {
+            throw new GlResourceConstructionException(
+                message,
+                this,
+                [constructionFailure, cleanupFailure]);
+        }
+
+        ExceptionDispatchInfo.Capture(constructionFailure).Throw();
+        throw new InvalidOperationException("Unreachable construction rollback path.");
+    }
 }