Function validate_bootstrap_edit 

pub fn validate_bootstrap_edit(
    proposed_source: &str,
    author: &EditAuthor,
    previous_policy: Option<&BootstrapPolicy>,
) -> BootstrapValidation

Validate a proposed edit to meta-invariants.harn.

• Archivist authorship is a hard Block with the stable code bootstrap_archivist_cannot_author_bootstrap.
• Otherwise, the proposed source is parsed for structural problems. If parsing fails, the result is Block.
• Clean proposals from a non-Archivist author yield RequireApproval, routed to one of the maintainers listed in the previous policy (or the default maintainer role on initial seed). The previous policy’s hash and the proposed policy’s hash are both pinned in the result so the slice approval chain has explicit audit pointers.