test(catalog): wire databases, security, delivery, and ai categories

The catalog now holds 250 tests across 8 categories and 25
subcategories, each with at least 10 tests.

internal/tests/catalog.go

@@ -19,5 +19,9 @@ func All() *testkit.Registry {
 	registerWhitepapersTests(r)
 	registerCodebaseTests(r)
 	registerAgentsTests(r)
+	registerDatabasesTests(r)
+	registerSecurityTests(r)
+	registerDeliveryTests(r)
+	registerAITests(r)
 	return r
 }

internal/tests/catalog_test.go

@@ -68,6 +68,10 @@ func TestAll_SubcategoryMinimums(t *testing.T) {
 		"operations":  {"macos", "linux", "kubernetes"},
 		"research":    {"web", "whitepapers", "codebase"},
 		"agents":      {"tool-routing", "planning", "delegation"},
+		"databases":   {"postgres", "redis", "sql-tuning"},
+		"security":    {"appsec", "crypto", "secrets"},
+		"delivery":    {"git", "containers", "release-engineering"},
+		"ai":          {"vector-search", "llm-integration", "rag"},
 	}
 
 	counts := make(map[string]map[string]int)