Add try-with-resources guideline to AGENTS.md

- Added bullet point under 'Leverage Java 21+ features' section
- Specifies that try-with-resources must be used for all AutoCloseable resources
- Includes examples like HttpClient and streams
- Ensures proper resource management following Java best practices

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: simbo1905

AGENTS.md

@@ -455,6 +455,7 @@ IMPORTANT: Never disable tests written for logic that we are yet to write we do
     * Pattern matching for structural decomposition
     * Sealed classes for exhaustive switches
     * Virtual threads for concurrent processing
+    * **Use try-with-resources for all AutoCloseable resources** (HttpClient, streams, etc.)
 
 ## Package Structure