Revert "feat(render): Phase A8 — wire stencil pipeline into render frame"

This reverts commit 41c2e67cd8.

src/AcDream.App/Rendering/CellVisibility.cs

@@ -344,17 +344,6 @@ public sealed class CellVisibility
                local.Z <= cell.LocalBoundsMax.Z + PointInCellEpsilon;
     }
 
-    /// <summary>
-    /// Looks up a loaded cell by full 32-bit cell id, or returns null if
-    /// not loaded. Used by the Phase A8 stencil pipeline to materialize
-    /// <see cref="VisibilityResult.VisibleCellIds"/> back into
-    /// <see cref="LoadedCell"/> instances for portal mesh extraction.
-    /// </summary>
-    public LoadedCell? TryGetCell(uint cellId)
-    {
-        return _cellLookup.TryGetValue(cellId, out var cell) ? cell : null;
-    }
-
     /// <summary>
     /// Brute-force scan of every loaded cell to test whether
     /// <paramref name="worldPoint"/> is inside any of them. Does not touch