Improve dimension mismatch warning for CDC Flow Matching

- Add explicit warning and tracking for multiple unique latent shapes
- Simplify test imports by removing unused modules
- Minor formatting improvements in print statements
- Ensure log messages provide clear context about dimension mismatches

library/cdc_fm.py

@@ -354,9 +354,11 @@ class LatentBatcher:
             Dict mapping exact_shape -> list of samples with that shape
         """
         batches = {}
+        shapes = set()
 
         for sample in self.samples:
             shape_key = sample.shape
+            shapes.add(shape_key)
 
             # Group by exact shape only - no aspect ratio grouping or resizing
             if shape_key not in batches:
@@ -364,6 +366,15 @@ class LatentBatcher:
 
             batches[shape_key].append(sample)
 
+        # If more than one unique shape, log a warning
+        if len(shapes) > 1:
+            logger.warning(
+                "Dimension mismatch: %d unique shapes detected. "
+                "Shapes: %s. Using Gaussian fallback for these samples.",
+                len(shapes),
+                shapes
+            )
+
         return batches
 
     def _get_aspect_ratio_key(self, shape: Tuple[int, ...]) -> str: