Organize legacy DRAFTS checkpoints

Move the four ResNet-era checkpoints into legacy/ and keep only the two current runtime checkpoints at the repository root.

README.md

@@ -45,9 +45,16 @@ deployment notes are maintained in the
 
 ## Legacy checkpoints
 
-The ResNet-18/ResNet-50 detector and classifier files remain available for
-reproducing earlier DRAFTS experiments. They are not the defaults of the
-current runtime.
+Earlier ResNet detector and classifier checkpoints are grouped under
+[`legacy/`](legacy/). They remain available for reproducing older DRAFTS
+experiments, but they are not used by the current runtime.
+
+| Task | File |
+|---|---|
+| CenterNet ResNet-18 detector | [`legacy/cent_resnet18.pth`](legacy/cent_resnet18.pth) |
+| CenterNet ResNet-50 detector | [`legacy/cent_resnet50.pth`](legacy/cent_resnet50.pth) |
+| ResNet-18 binary classifier | [`legacy/class_resnet18.pth`](legacy/class_resnet18.pth) |
+| ResNet-50 binary classifier | [`legacy/class_resnet50.pth`](legacy/class_resnet50.pth) |
 
 ## License and citation