feat(cursor): The open Posts should reliably be available in a Cursor context

[joelhooks]

Right now you can find the posts to add to a Cursor context, but it isn't using the currently open window, it's pulling it from someplace else (undetermined)

Initial theory is that we could tighten up the way we use the file system and represent open Builder Posts as URIs (builder://${slug}) mapped to a folder in the users home directory

related, the open tab isn't always the post even though it will appear to be the post.

Being able to reliably add an open Post to context would allow you to write/edit a post in the context of a currently open codebase or set of files. This would let cursor pull code snippets etc.