tools: use ResourceId.parent_folder()

Fixes: #206

docs/changelog.rst

@@ -8,6 +8,7 @@ Changelog
 
 * Items in the Project Browser can now be sorted by name, type, size or last modification time.
 * Added a list-view mode to the Project Browser.
+* Fixed an issue that caused erratic resources being shown in the Project Brower's folder view.
 
 0.53.0 --- 30 Nov 2024
 ----------------------

tools/level_editor/project_browser.vala

@@ -1366,7 +1366,7 @@ public class ProjectBrowser : Gtk.Bin
 						return false;
 
 					// Skip paths without common ancestor.
-					if (!name.has_prefix(selected_name))
+					if (ResourceId.parent_folder(name) != selected_name)
 						return false;
 
 					// Skip paths that are too deep in the hierarchy: