ci(links): add link checking with lychee

- Configure lychee for notebook link validation
- Set up GitHub workflow for PR and scheduled checks
- Exclude API endpoints and localhost from checks
- Add PR comment integration for broken links

.github/workflows/links.yml

@@ -0,0 +1,65 @@
+name: Link Check
+
+on:
+  pull_request:
+    types: [opened, synchronize]
+  schedule:
+    - cron: "0 0 * * SUN"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  check-links:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+      
+      - name: Convert notebooks for link extraction
+        run: |
+          pip install jupyter nbconvert
+          mkdir -p temp_md
+          
+          for nb in skills/**/*.ipynb; do
+            echo "Converting: $nb"
+            jupyter nbconvert --to markdown "$nb" \
+              --output-dir=temp_md \
+              --ExtractOutputPreprocessor.enabled=False
+          done
+      
+      - name: Check Links with Lychee
+        id: lychee
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: |
+            --config lychee.toml 
+            --format markdown
+            --output lychee-report.md
+            --no-progress
+            skills/**/*.md 
+            temp_md/*.md 
+            README.md
+          fail: false
+      
+      - name: Comment PR with results
+        if: github.event_name == 'pull_request' && steps.lychee.outputs.exit_code != 0
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          header: link-check
+          path: lychee-report.md
+      
+      - name: Upload link check results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: link-check-results
+          path: |
+            lychee-report.md
+            .lycheecache

lychee.toml

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+# Lychee configuration for Anthropic Cookbook
+cache = true
+max_cache_age = "1d"
+timeout = 30
+max_redirects = 10
+max_retries = 3
+retry_wait_time = 2
+include_fragments = true
+skip_missing = false
+
+# Jupyter-specific settings
+glob_ignore_case = true
+fallback_extensions = ["ipynb", "md", "html", "py"]
+
+exclude_path = [
+    ".git/",
+    "__pycache__/",
+    ".ipynb_checkpoints/",
+    "*.pyc"
+]
+
+exclude = [
+    "https://api.anthropic.com.*",
+    "https://console.anthropic.com.*",
+    "http://localhost.*",
+    "http://127.0.0.1.*"
+]
+
+# Accept these status codes
+accept = [200, 201, 202, 203, 204, 206, 301, 302, 303, 304, 307, 308, 403, 429]
+
+# Headers for authenticated requests
+headers = [
+    "User-Agent=Mozilla/5.0 (compatible; lychee/0.20.1; anthropic-cookbook)"
+]