[pasrom]

What

A doc can now say who may sign it off.

approval	Who may sign off
unset or human	a person (initials in approved_by)
ai	an AI review alone is enough, written approved_by: "ai:<model>"
any value, on audience: customer or type: verbatim-block	always a person; approval: ai there is an error

• km approve <doc>... --by WHO [--at DATE] [--review-by DATE]:
  • moves a review doc to the served status and writes approved_by / approved_at in place, then gates it with km validate;
  • refuses, before writing, what the level forbids, a non-review doc, and a review_by that has passed or can't be parsed, since the next km demote would undo the approval;
  • restores a refused doc byte for byte.
• km validate:
  • fails a signed-off doc whose ai: approver its level does not allow, keyed on the configured served status;
  • the rule lives once in km.common.approval_problem, shared with approve.
• reviewed_by (list): records pre-reviews, such as a PR bot's model, date and PR. It is not an approval. promote and --replace drop it with the approval. A cross-repo promote also drops approval, so the target decides its own level.
• status_rules:
  • keys are read generically as <status>_<requires|recommends|forbids>, so accepted_requires needs no code of its own;
  • a malformed key, or a brain key naming an unknown status, fails fast;
  • km's own keys stay valid in a brain that renames its statuses.
• Team template: requires owner and review_by for accepted docs, which its CONVENTIONS already stated.

It is metadata, not authentication, like the rest of the gate.

Verification

• All four smoke suites pass: gate 80, index 30, team 96, encoding 4.
• Every rule was mutation-checked in both directions, and each mutation fails at least one test.
• Positive control on a real team brain:
  • ai: without approval: ai is refused before writing;
  • with it, km approve signs the doc off;
  • removing approval: ai afterwards fails km validate.
• /simplify ran, then three review passes. The findings are fixed and each has a test:
  • served status keyed on the literal word;
  • a stale review_by accepted, including through a backdated --at or a past --review-by;
  • a misspelled status in status_rules silently ignored;
  • a BOM lost on restore;
  • CRLF docs rejected;
  • an unparseable review_by passing.

Not changed

• A successful approve writes UTF-8 with LF, like every km write.
• km demote keeps reviewed_by, since the text it describes has not changed.