define Tags vision

we will soon add Tags feature in #65

I think it could be good to think about what game-design possibilites we would want to handle with it -> from easy to crazy cool ideas !

the goal is to construct a bit more our vision about the Game

No files or tests are named in this issue. Start by reading the referenced issue #65 to learn the planned Tags feature scope. Then scan the repo for any existing gameplay/design documentation to anchor a concrete vision proposal (goals, expected behaviors, and limits for tags). Done means a clear, actionable design brief that can be split into specific implementation issues.

索引モデルが issue の本文から書いたものです。