Add README with per-config metadata

README.md

@@ -27,12 +27,15 @@ subset is a separate config in HuggingFace `imagefolder` format (images +
 `metadata.jsonl`). Every row has an `image`, a `prompt`, and a `correct_option`
 (A/B/C/D).
 
+All four subsets are **step-completion** tasks: given a partial sequence (with one
+erroneous step) and an image, select the option that correctly completes the task.
+
 | Config | Items | Task |
 |--------|-------|------|
-| `checkboard`   | 4896 | Grid path planning around obstacles |
-| `blocksworld`  | 5000 | Block-stacking move-sequence selection |
-| `imagenet`     | 1000 | Image-patch rearrangement validation |
-| `robovqa`      |  300 | Robot action-sequence selection |
+| `checkboard`   | 4891 | Complete the path from start to goal around obstacles |
+| `blocksworld`  | 5000 | Complete the block-move sequence to the target configuration |
+| `imagenet`     | 5000 | Complete the patch-swap sequence to rearrange into the target image |
+| `robovqa`      |  390 | Complete the robot action sequence |
 
 ## Usage