Rewrite Lake Wash proposal

We can model it properly as access restrictions now, and can maybe fit to the template better

Find the Lake Wash proposal document in the repository, likely in a proposals or docs directory. Understand the current template structure and what 'access restrictions' mean in the context of A/B Street. Rewrite the proposal to align with the template and properly model access restrictions.

索引モデルが issue の本文から書いたものです。