feat(guide): add thinking keywords, GitHub Actions examples, and improvement recommendations

Documentation enhancements:
- Add inline thinking keywords section (think, think hard, ultrathink) with usage examples
- Create examples/github-actions/ directory with 3 ready-to-use workflows:
  * Auto PR review with inline comments
  * Security review on every PR
  * Issue triage with label suggestions
- Add comprehensive IMPROVEMENT_RECOMMENDATIONS.md with prioritized action items

Improvements based on zebbern/claude-code-guide analysis:
- Enhanced troubleshooting guidance
- Format enhancements (badges, collapsible tables, C-style comments)
- Security/performance/workflow pitfalls sections
- DeepSeek integration documentation
- One-shot health check scripts

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

examples/github-actions/claude-security-review.yml

@@ -0,0 +1,26 @@
+name: Security Review
+on:
+  pull_request:
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  security:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha || github.sha }}
+          fetch-depth: 2
+
+      - name: Claude Code Security Review
+        uses: anthropics/claude-code-security-review@main
+        with:
+          claude-api-key: ${{ secrets.ANTHROPIC_API_KEY }}
+          comment-pr: true
+          # Optional configuration:
+          # exclude-directories: "docs,examples"
+          # claudecode-timeout: "20"
+          # claude-model: "claude-3-5-sonnet-20240620"