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/GameRenderResourceLifetime.cs

@@ -1,10 +1,15 @@
 namespace AcDream.App.Rendering;
 
+internal interface IGameRenderResourceLifetime
+{
+    TerrainAtlas AcquireTerrainAtlas(Func<TerrainAtlas> factory);
+}
+
 /// <summary>
 /// Sole lifetime owner for render resources that are borrowed by, but not
 /// owned by, their renderers.
 /// </summary>
-internal sealed class GameRenderResourceLifetime
+internal sealed class GameRenderResourceLifetime : IGameRenderResourceLifetime
 {
     private readonly OwnedResourceSlot<TerrainAtlas> _terrainAtlas = new();
     private readonly OwnedResourceSlot<Shader> _skyShader = new();