fix(ci): add missing SPDX headers to workflow files

The Governance reusable's "Workflow security linter" job requires every
.github/workflows/*.yml to carry an SPDX-License-Identifier on line 1. These
files were missing it, so the Governance workflow failed on every push — one
more red workflow feeding the ci_activity notification flood.

Identifier (MPL-2.0) is taken from this repo's own existing workflow headers,
which agree unanimously — not assumed. Files: boj-build.yml casket-pages.yml ci.yml codeql.yml docker-publish.yml instant-sync.yml integration-tests.yml mirror.yml pages.yml rescript-deno-ci.yml secret-scanner.yml workflow-linter.yml

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/boj-build.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 name: BoJ Server Build Trigger

.github/workflows/casket-pages.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 name: GitHub Pages

.github/workflows/ci.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 permissions:

.github/workflows/codeql.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 name: CodeQL Security Analysis

.github/workflows/docker-publish.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 name: Docker Build and Publish

.github/workflows/instant-sync.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 # Instant Forge Sync - Triggers propagation to all forges on push/release

.github/workflows/integration-tests.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 name: Integration Tests

.github/workflows/mirror.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 name: Mirror to Git Forges

.github/workflows/pages.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 name: GitHub Pages (Ddraig SSG)
 on:
   push:

.github/workflows/rescript-deno-ci.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # // Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 # SPDX-License-Identifier: MPL-2.0
 permissions: