Keys per namespace: key_close, D7, first policy; remove carried_over; the two notices #149

Issue 6 of ledger/prd/namespace-independence-prd.md §6, opened on the principal's instruction (session ledger/sessions/2026-10-namespace-layout-authority.md).

Cites. PRD §3.3 (Keys).

Size. M. Depends on. Issue 5.

Appendix C note. Yes.

Rulings carried. 47, 69 (a close in every namespace a writer holds is one change-set per namespace in one commit; a key closed in one namespace and open in another is a notice, never a finding).

What it builds. The functions of authority::key_close compare namespace: a close ends the key in its own namespace only (LP-6.32); "a key belongs to one principal" and "a closed key is never bound again" are judged within the namespace. The genesis holder's first key in a namespace is that namespace's self-bound binding, trusted by today's rule for the first namespace; signing::check::carried_over and the store-wide branch of authority::filing::may_file go away; a first policy is signed by a key trusted in its own namespace only. Two repository notices: a key closed in one namespace and open in another; one key bound to two principals in two namespaces. Protocol: LP-4.31, LP-4.37, LP-4.39 (with ruling 101's wording), LP-4.13, LP-6.32 loses its mark; Appendix B row; Appendix C note. ledger-cli/tests/key_across_namespaces.rs's six tests are rewritten as §3.11 says. The step also carries the test that no agent identity and no non-interactive session can produce a key close.

Acceptance criteria (§4.1).

• AC-47 (second bullet). A rotate in A leaves B's acceptances, review items and allowed_signers unchanged.

Related open issues: #104 (part 1, implemented store-wide; this issue narrows it to the namespace) and #105 (part 2; the writer half is issue 8 of the PRD).