fix: move task.md files to correct commands directories

- Move task.md from command-ja/ to commands-ja/
- Move task.md from command-en/ to commands-en/
- Correct directory naming to match existing convention

The files were accidentally placed in incorrect directories (command-*)
instead of the proper commands-* directories.

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: shinpr