Document GuiListView bug fix in implementation plan

Add technical notes about the raygui GuiListView return value bug
and the solution implemented.

docs/ui_implementation_plan.md

@@ -115,6 +115,22 @@ All phases have been successfully implemented. See `docs/ui_implementation_summa
 - ✅ Minimal state management required
 - ✅ Follows existing dependency patterns (git submodules)
 
+## Bug Fixes
+
+### GuiListView Return Value Bug (FIXED)
+**Issue**: GuiListView() always returns 0 (known raygui bug), preventing body selection from working.
+
+**Solution**:
+- Added `body_list_scroll` and `body_list_active` to RenderState for state persistence
+- Check `body_list_active` parameter changes instead of return value
+- Initialize `body_list_active` to -1 in main.cpp
+
+**Reference**: https://github.com/raysan5/raygui/issues/448
+
+**Commits**:
+- `85bd9ee`: Fix raygui body selection - GuiListView return value bug
+- `1b8e092`: Improve buffer safety in body list string construction
+
 ## Future Enhancements (Optional)
 
 ### Potential Improvements: