link checking on all md

.github/workflows/link-check.yml

@@ -0,0 +1,113 @@
+name: Link Checker
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+  workflow_dispatch:
+
+jobs:
+  link-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Restore lychee cache
+        uses: actions/cache@v4
+        with:
+          path: .lycheecache
+          key: cache-lychee-${{ github.sha }}
+          restore-keys: cache-lychee-
+
+      - name: Run Lychee link checker
+        uses: lycheeverse/lychee-action@v2
+        id: lychee
+        with:
+          # Check all markdown files
+          args: |
+            --cache
+            --max-cache-age 1d
+            --verbose
+            --no-progress
+            --exclude-mail
+            '**/*.md'
+          # Output results to file for parsing
+          output: lychee-output.md
+          # Don't fail the build on broken links (warning mode)
+          fail: false
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Parse link check results
+        id: parse-results
+        if: always()
+        run: |
+          # Initialize defaults
+          BROKEN="0"
+          TOTAL="0"
+
+          # Parse lychee output for statistics
+          if [ -f "lychee-output.md" ]; then
+            # Extract statistics from lychee output
+            TOTAL=$(grep -oP 'Total\s+\|\s+\K\d+' lychee-output.md || echo "0")
+            BROKEN=$(grep -oP 'Errors\s+\|\s+\K\d+' lychee-output.md || echo "0")
+
+            # If stats not found in that format, try alternate parsing
+            if [ "$TOTAL" = "0" ] && [ "$BROKEN" = "0" ]; then
+              BROKEN=$(grep -c "❌\|✗\|ERROR" lychee-output.md || echo "0")
+            fi
+          fi
+
+          # Set status based on results
+          if [ "$BROKEN" = "0" ]; then
+            STATUS_ICON="✅"
+            STATUS_TEXT="All links are working!"
+            COLOR="#36a64f"
+          else
+            STATUS_ICON="⚠️"
+            STATUS_TEXT="Found $BROKEN broken link(s)"
+            COLOR="#ffa500"
+          fi
+
+          # Extract broken links for summary (limit to first 15 lines)
+          BROKEN_LINKS=""
+          if [ -f "lychee-output.md" ] && [ "$BROKEN" != "0" ]; then
+            # Get the errors section from lychee output
+            BROKEN_LINKS=$(awk '/## Errors/,/^$/' lychee-output.md | grep -E "^\*|http|^  " | head -15 || echo "")
+
+            # If no errors section found, try to extract failed URLs
+            if [ -z "$BROKEN_LINKS" ]; then
+              BROKEN_LINKS=$(grep -B 1 "❌\|✗\|ERROR" lychee-output.md | head -15 || echo "")
+            fi
+          fi
+
+          # Export for Slack notification
+          echo "STATUS_ICON=$STATUS_ICON" >> $GITHUB_ENV
+          echo "STATUS_TEXT=$STATUS_TEXT" >> $GITHUB_ENV
+          echo "COLOR=$COLOR" >> $GITHUB_ENV
+          echo "BROKEN_COUNT=$BROKEN" >> $GITHUB_ENV
+          echo "TOTAL_COUNT=$TOTAL" >> $GITHUB_ENV
+
+          # Save broken links to multiline env var
+          {
+            echo 'BROKEN_LINKS<<EOF'
+            echo "$BROKEN_LINKS"
+            echo 'EOF'
+          } >> $GITHUB_ENV
+
+      - name: Send results to Slack
+        if: always()
+        uses: rtCamp/action-slack-notify@v2
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}
+          SLACK_CHANNEL: ${{ vars.SLACK_CHANNEL }}
+          SLACK_TITLE: "🔗 Link Check Results"
+          SLACK_COLOR: ${{ env.COLOR }}
+          SLACK_MESSAGE: |
+            *Status:* ${{ env.STATUS_ICON }} ${{ env.STATUS_TEXT }}
+            *Total Links Checked:* ${{ env.TOTAL_COUNT }}
+            *Broken Links Found:* ${{ env.BROKEN_COUNT }}
+
+            ${{ env.BROKEN_COUNT != '0' && format('*Sample Broken Links:*\n```\n{0}\n```\n\n_See full details in the workflow run_', env.BROKEN_LINKS) || '' }}
+
+            *Run Details:* ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}