Function check_scope_allows_create 

pub fn check_scope_allows_create(
    scope: Option<&str>,
    root_id: Option<&str>,
) -> Result<(), Error>

Check if a scoped token allows write access for file creation.

For scoped tokens, file creation is only allowed when:

• The scope grants Write access
• The file has a root_id that matches the scope’s file_id (i.e., the new file is a child in the scoped document tree)

Returns Ok(()) if allowed, Err if denied.