Update developer guide to clarify support for parent/child hierarchies and distance-based entity queries

docs/DEVELOPER_GUIDE.md

@@ -1,6 +1,10 @@
 # Starworld Developer Quick Reference
 
 ## Build Commands
+#
+# Entity System Features
+# - Parent/child entity hierarchies are fully supported (scene graph, transform propagation)
+# - Entity query/filtering by distance is available via C++/Rust bridge API
 
 ```bash
 # Full clean build