Fix CI workflows and installation documentation

- Replace non-existent anthropics/claude-code-action@v1 with direct bash steps in smart-sync.yml and pr-issue-auto-close.yml
- Add missing checkout steps to both workflows for WORKFLOW_KILLSWITCH access
- Fix Issue #189: Replace broken 'npx ai-agent-skills install' with working 'npx agent-skills-cli add' command
- Update README.md and INSTALLATION.md with correct Agent Skills CLI commands and repository links
- Verified: agent-skills-cli detects all 53 skills and works with 42+ AI agents

Fixes: Two GitHub Actions workflows that broke on PR #191 merge
Closes: #189

.github/workflows/pr-issue-auto-close.yml

@@ -17,6 +17,9 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
       - name: Check Workflow Kill Switch
         run: |
           if [ -f ".github/WORKFLOW_KILLSWITCH" ]; then