chore: clarify .sandbox directory in gitignore

• Add comment explaining sandbox directory is for testing
• Note that only scripts are tracked, not sandbox contents

Author: SatanshuMishra

.gitignore

@@ -36,6 +36,7 @@ coverage/
 *.lcov
 
 # Testing
+# Sandbox directory for testing Labcommitr commands (scripts in scripts/ are tracked)
 .sandbox/
 test-results/
 
@@ -68,6 +69,7 @@ Thumbs.db
 .cache/
 
 
+
 ### Other
 # Remove rust files for now
 rust-src/