licence(#7): normalise PMPL-1.0 -> PMPL-1.0-or-later (owner carve-out, SPDX-only) (#18)

Not a relicence; owner-sanctioned standards LICENCE-POLICY A8(1).
Refs LICENCE-DEBT-LEDGER-2026-05-18.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath