chore(.machine_readable): convert 6a2 checkpoint files from Scheme to A2ML

Convert all .machine_readable/6a2/ files from Guile Scheme format to
A2ML (a2ml) format. Preserves all data (project name, version, milestones,
blockers, actions) in the A2ML TOML-like structure.

Also fills in unfilled template placeholders ({{CURRENT_YEAR}}, {{AUTHOR}},
etc.) with concrete values.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hyperpolymath

.machine_readable/6a2/AGENTIC.a2ml

@@ -1,12 +1,12 @@
 # SPDX-License-Identifier: PMPL-1.0-or-later
-# Copyright (c) {{CURRENT_YEAR}} {{AUTHOR}} ({{OWNER}}) <{{AUTHOR_EMAIL}}>
+# Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
 #
 # AGENTIC.a2ml — AI agent constraints and capabilities
 # Defines what AI agents can and cannot do in this repository.
 
 [metadata]
 version = "0.1.0"
-last-updated = "{{CURRENT_DATE}}"
+last-updated = "2026-04-11"
 
 [agent-permissions]
 can-edit-source = true

.machine_readable/6a2/NEUROSYM.a2ml

@@ -1,12 +1,12 @@
 # SPDX-License-Identifier: PMPL-1.0-or-later
-# Copyright (c) {{CURRENT_YEAR}} {{AUTHOR}} ({{OWNER}}) <{{AUTHOR_EMAIL}}>
+# Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
 #
 # NEUROSYM.a2ml — Neurosymbolic integration metadata
 # Configuration for Hypatia scanning and symbolic reasoning.
 
 [metadata]
 version = "0.1.0"
-last-updated = "{{CURRENT_DATE}}"
+last-updated = "2026-04-11"
 
 [hypatia-config]
 scan-enabled = true

.machine_readable/6a2/PLAYBOOK.a2ml

@@ -1,12 +1,12 @@
 # SPDX-License-Identifier: PMPL-1.0-or-later
-# Copyright (c) {{CURRENT_YEAR}} {{AUTHOR}} ({{OWNER}}) <{{AUTHOR_EMAIL}}>
+# Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
 #
 # PLAYBOOK.a2ml — Operational playbook
 # Runbooks, incident response, deployment procedures.
 
 [metadata]
 version = "0.1.0"
-last-updated = "{{CURRENT_DATE}}"
+last-updated = "2026-04-11"
 
 [deployment]
 # method = "gitops"  # gitops | manual | ci-triggered