ci: check every link in the Markdown files [PANL-014]

.github/workflows/links.yml

@@ -0,0 +1,29 @@
+name: links
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+  schedule:
+    - cron: '41 6 * * 1'   # weekly, Monday: catches links that rot after publishing
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  links:
+    name: check links
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - name: Check every link in the Markdown files
+        uses: lycheeverse/lychee-action@v2.9.0
+        with:
+          # 429 means "slow down", not "broken". LinkedIn answers bots with 999, so it is skipped.
+          args: >-
+            --no-progress --max-retries 3 --timeout 20
+            --accept 200,206,429
+            --exclude 'linkedin\.com'
+            './**/*.md'
+          fail: true