Fix: type filter plural mismatch (Classes vs Class), add exhaustive public tests

Fix pre-existing bug where filter buttons (Classes/Properties/Individuals)
never matched because currentFilter was 'classes' but entity type text was
'Class'. Now handles singular/plural comparison correctly.

Add 65-test exhaustive Playwright suite for the public site covering every
click route: welcome panel, module pills, sidebar navigation, search,
type filters, entity details, relationships, breadcrumbs, back-to-welcome,
featured cards, URL parameters, cross-module navigation, and visual integrity.

Author: styk-tv

docs/public/browse/ontology-manager.js

@@ -766,7 +766,11 @@ class OntologyManager {
                 const type = entityItem.querySelector('.entity-type').textContent;
 
                 const matchesSearch = !query || label.includes(query) || uri.includes(query);
-                const matchesFilter = this.currentFilter === 'all' || type.toLowerCase() === this.currentFilter;
+                const typeLower = type.toLowerCase();
+                const matchesFilter = this.currentFilter === 'all' ||
+                    typeLower === this.currentFilter ||
+                    typeLower + 's' === this.currentFilter ||
+                    typeLower + 'es' === this.currentFilter;
 
                 const isVisible = matchesSearch && matchesFilter;
                 entityItem.style.display = isVisible ? 'flex' : 'none';