fix: SPDX headers (AGPL→PMPL), email, author name

- AGPL-3.0-or-later → PMPL-1.0-or-later in SPDX-License-Identifier lines
- jonathan.jewell@open.ac.uk → j.d.a.jewell@open.ac.uk
- "hyperpolymath" → "Jonathan D.A. Jewell" in author fields

Part of global TODO cleanup (2026-03-16).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

SECURITY.md

@@ -37,7 +37,7 @@ This method ensures:
 
 If you cannot use GitHub Security Advisories, you may email us directly at:
 
-**Email:** jonathan.jewell@open.ac.uk
+**Email:** j.d.a.jewell@open.ac.uk
 
 > **⚠️ Important:** Do not report security vulnerabilities through public GitHub issues, pull requests, discussions, or social media.