fix: Resolve markdown linting errors in codebase-agent.md

Fix 5 markdownlint errors:
- MD031: Add blank lines around fenced code blocks
- MD032: Add blank lines before lists
- MD024: Rename duplicate "Troubleshooting" to "GitHub Actions Troubleshooting"

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

Author: jeremyeder

docs/patterns/codebase-agent.md

@@ -306,13 +306,15 @@ message = client.messages.create(
 ```
 
 Update dependencies:
+
 ```bash
 pip install google-cloud-aiplatform anthropic[vertex]
 ```
 
 ### Security
 
 **What This Protects:**
+
 - ✅ No service account keys (Workload Identity Federation)
 - ✅ Attribute-based access control (only your repo)
 - ✅ Short-lived tokens (1 hour expiry)
@@ -337,7 +339,7 @@ concurrency:
     fi
 ```
 
-### Troubleshooting
+### GitHub Actions Troubleshooting
 
 | Error | Cause | Fix |
 |-------|-------|-----|
@@ -349,6 +351,7 @@ concurrency:
 ### Cost Estimate
 
 **Vertex AI (Claude 3.5 Sonnet)**:
+
 - Input: $3.00/1M tokens
 - Output: $15.00/1M tokens
 - Average PR review: ~$0.03
@@ -362,6 +365,7 @@ concurrency:
 ![Screenshot: User adds "cba-review" label to PR]
 
 **Bot posts review:**
+
 ```markdown
 ## 🤖 Codebase Agent