docs: add validation section to README

Document the validate.sh script functionality:

- Add Validation section after SSL Stack components
- Describe script usage and invocation
- List validation checks performed:
  - Required top-level files and directories
  - Initializer directory structure
  - Apply script syntax
  - Path consistency between apply scripts and configs/scripts

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README.md

@@ -179,6 +179,20 @@ Available on development workstations or when `COMPILE_SSL_STACK=true`:
 - Apache HTTPd with HTTP/2 enabled
 - Custom installations at `/usr/local/custom-ssl/`
 
+## Validation
+
+The repository includes a validation script to verify structure and configuration:
+
+```bash
+./validate.sh
+```
+
+This checks:
+- Required top-level files and directories
+- Initializer directory structure
+- Apply script syntax
+- Path consistency between apply scripts and configs/scripts directories
+
 ## Troubleshooting
 
 For detailed status information: