Cube3D: route VAE decode through managed comfy.sd.VAE.decode

Stop fighting ComfyUI's model management. VAEDecodeCube was manually
calling load_models_gpu + .to(vae.device) and the VAE forced
disable_offload=True because it bypassed the managed decode path.

Now CubeShapeVAE.decode(samples) is the entry point that comfy.sd.VAE.decode
calls, so loading/device/dtype are handled automatically (like Hunyuan3Dv2):
- removed disable_offload=True (let the offload system manage weights)
- removed manual load_models_gpu + .to(device) from the node
- process_output set to identity (default clamps [0,1] in-place and would
  destroy the occupancy isosurface)
- decode() pre-inverts VAE.decode's trailing movedim(1,-1) so the node
  receives grid logits unchanged (parity preserved)
- memory_used_decode sized by num_tokens (shape[-1]) for the new latent layout

Amp-Thread-ID: https://ampcode.com/threads/T-019ec361-addb-70d8-a74b-438ce8a1e096
Co-authored-by: Amp <amp@ampcode.com>

comfy/ldm/cube/vae.py

@@ -288,6 +288,9 @@ def generate_dense_grid_points(bbox_min, bbox_max, resolution_base, indexing="ij
 class CubeShapeVAE(nn.Module):
     """Decode-only OneDAutoEncoder. Encoder weights load with strict=False (ignored)."""
 
+    # Fixed query bounds for the occupancy grid (upstream default).
+    decode_bounds = (-1.05, -1.05, -1.05, 1.05, 1.05, 1.05)
+
     def __init__(self, num_encoder_latents=1024, embed_dim=32, width=768, num_heads=12,
                  num_freqs=128, num_decoder_layers=24, num_codes=16384, out_dim=1, eps=1e-6,
                  dtype=None, device=None):
@@ -303,6 +306,19 @@ class CubeShapeVAE(nn.Module):
         self.occupancy_decoder = OneDOccupancyDecoder(self.embedder, out_dim, width, num_heads,
                                                       eps=eps, dtype=dtype, device=device)
 
+    @torch.no_grad()
+    def decode(self, samples, resolution_base=8.0, chunk_size=100_000, **kwargs):
+        """Token IDs -> occupancy grid logits. Entry point for comfy.sd.VAE.decode, which
+        manages model loading/device/dtype. `samples` arrive as (B, 1, num_tokens) in the
+        VAE working dtype on the load device. VAE.decode applies a trailing movedim(1, -1),
+        so pre-invert it here to hand the node grid logits as (B, gx, gy, gz)."""
+        ids = samples.reshape(samples.shape[0], -1)[:, :self.cfg_num_encoder_latents]
+        ids = ids.round().long().clamp(0, self.cfg_num_codes - 1)
+        latents = self.decode_indices(ids)
+        grid_logits, _, _, _ = self.extract_geometry(
+            latents, bounds=self.decode_bounds, resolution_base=resolution_base, chunk_size=chunk_size)
+        return grid_logits.movedim(-1, 1)
+
     @torch.no_grad()
     def decode_indices(self, shape_ids):
         z_q = self.bottleneck.block.lookup_codebook(shape_ids)