fix(licence): canonicalise to PMPL-1.0-or-later per authorship check (#133) (#34)

Refs hyperpolymath/standards#133 / standards#124. NOT Closes
(proof-debt — main soundness/rescue-branch — is separate).

Authorship check (git shortlog + per-file git log): every affected
file is 100% owner-own (Jonathan D.A. Jewell); dependabot touched only
CI; nothing vendored/third-party; no AGPL-by-intent. The
"AGPL-3.0 / Palimpsest 0.5" strings are scaffold-placeholder drift
(the ledger root cause), not a deliberate election. Owner-ruled.

- 13 proof files: `License: AGPL-3.0 / Palimpsest 0.5`
  -> `License: PMPL-1.0-or-later` (matches the 2 already-correct files
  CNOCategory.v / LambdaCNO.v; ledger rule #5 + stale-Palimpsest->PMPL).
- 4 missing-header files (owner-own): added the canonical header —
  StatMech_helpers.v in the repo proof-file doc-comment form
  (Author/Project/License), src/main.rs + src/brainfuck/src/main.rs +
  src/AuditTrail.res with the estate SPDX+Copyright form (CLAUDE.md
  requires SPDX headers on all files).
- Deleted the 0-byte LICENSE-PALIMPS.txt stub: NOT referenced by root
  LICENSE (which references EXHIBIT-A/B), and the repo's own audit
  trail (LICENSE-AUDIT-2026-02-05.adoc, ROADMAP, SESSION-COMPLETE)
  already prescribes its removal. Canonical text remains in
  license/PMPL-1.0.txt and root LICENSE.

Header-only; no proof semantics touched (build/soundness state is the
separate standards#133 proof-debt item — the unmerged rescue branch).

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

Author: hyperpolymath