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: ada.yml codeql.yml comprehensive-quality.yml generator-generic-ossf-slsa3-publish.yml instant-sync.yml mirror.yml pages.yml secret-scanner.yml workflow-linter.yml

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

Author: hyperpolymath

.github/workflows/ada.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: Ada (GNAT)

.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/comprehensive-quality.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: Comprehensive Quality Gates

.github/workflows/generator-generic-ossf-slsa3-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
 # This workflow uses actions that are not certified by GitHub.

.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/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/secret-scanner.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
 # Prevention workflow - scans for hardcoded secrets before they reach main

.github/workflows/workflow-linter.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
 # Prevention workflow - validates all workflows have proper security config