Restructure for multi-config: default/ and claude/ subdirectories

- Moved coding_excellence_ja.jsonl → default/train/
- Moved coding_excellence_ja_claude.jsonl → claude/train/
- Updated dataset_infos.json with new paths
- Updated README configs with new paths
- This enables load_dataset(..., 'default') and load_dataset(..., 'claude')

README.md

@@ -5,6 +5,15 @@ language:
 - ja
 license:
 - agpl-3.0
+configs:
+- config_name: default
+  data_files:
+  - split: train
+    path: default/train/coding_excellence_ja.jsonl
+- config_name: claude
+  data_files:
+  - split: train
+    path: claude/train/coding_excellence_ja_claude.jsonl
 ---
 
 # Coding Excellence 日本語版