chore(licence): normalise to MPL-2.0 + CC-BY-SA-4.0 (canonical pair) (#40)

Estate licence normalisation. LICENSES/={MPL-2.0,CC-BY-SA-4.0}; root
LICENSE=verbatim MPL-2.0 (GitHub display); code->MPL-2.0,
docs(.md/.adoc)->CC-BY-SA-4.0; vendored untouched. Residual mentions
(mostly legitimate anti-AGPL rules): 71. Manual-review licence PR.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.devcontainer/Containerfile

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-License-Identifier: MPL-2.0
 # Copyright (c) {{CURRENT_YEAR}} {{AUTHOR}} ({{OWNER}}) <{{AUTHOR_EMAIL}}>
 #
 # Dev Container image for {{PROJECT_NAME}}

.devcontainer/README.adoc

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: AGPL-3.0-or-later
+// SPDX-License-Identifier: MPL-2.0
 // Copyright (c) {{CURRENT_YEAR}} Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
 //
 // Dev Container configuration for {{PROJECT_NAME}}

.devcontainer/devcontainer.json

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-License-Identifier: MPL-2.0
 # Activate development environment
 # Install direnv: https://direnv.net/
 

.envrc

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-License-Identifier: MPL-2.0
 # RSR-compliant .gitattributes
 
 * text=auto eol=lf

.gitattributes

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-License-Identifier: MPL-2.0
 # CODEOWNERS - Define code review assignments
 # See: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners
 #

.github/CODEOWNERS

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-License-Identifier: MPL-2.0
 # Funding platforms for hyperpolymath projects
 # See: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/displaying-a-sponsor-button-in-your-repository