Fix Scratch event categories and color effect unit inputs

[oco777]

Summary

• move the "クローンされたとき" Scratch event unit into the FUnity/Scratch/イベント category with appropriate metadata
• document the updated category placement and clarify that the color effect unit resolves its actor from context
• drop the explicit actor input from "色の効果を○ずつ変える" and resolve the adapter via context to match Scratch behavior

Testing

• not run (not requested)

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Codex Task