feat(envcell): CellHasTransparent predicate (shell-batching prep)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -1053,6 +1053,29 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         }
     }
 
+    /// <summary>
+    /// True if the cell's prepared snapshot has any transparent render batch.
+    /// The pview shell pass uses this to skip the (heavy per-frame) transparent
+    /// <see cref="Render"/> call for opaque-only cells — most cell geometry is
+    /// opaque walls/floors/ceilings, so this removes the bulk of the per-cell
+    /// transparent draws. Read-only; mirrors the [shell] probe's batch scan.
+    /// </summary>
+    public bool CellHasTransparent(uint cellId)
+    {
+        var snapshot = _activeSnapshot;
+        if (snapshot is null || !snapshot.BatchedByCell.TryGetValue(cellId, out var gfxDict))
+            return false;
+        foreach (var (gfxObjId, transforms) in gfxDict)
+        {
+            if (transforms.Count == 0) continue;
+            var rd = _meshManager.TryGetRenderData(gfxObjId);
+            if (rd is null) continue;
+            foreach (var b in rd.Batches)
+                if (b.IsTransparent) return true;
+        }
+        return false;
+    }
+
     // ---------------------------------------------------------------------------
     // GetCellLightSet (A7 Fix D D-2 helper)
     // Per-cell up-to-8 point lights, cached per frame. Camera-independent, like