Fix oxlint warnings, extract dialog polyfill, deny warnings in gate

Adds void to floating promise in bestiary-cache.ts, extracts shared
polyfillDialog() helper to eliminate unbound-method warnings in 3 test
files. Adds --deny warnings to oxlint so future warnings fail the
build.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/adapters/bestiary-cache.ts

@@ -40,7 +40,7 @@ async function getDb(): Promise<IDBPDatabase | null> {
 				}
 				if (oldVersion < 2 && database.objectStoreNames.contains(STORE_NAME)) {
 					// Clear cached creatures to pick up improved tag processing
-					transaction.objectStore(STORE_NAME).clear();
+					void transaction.objectStore(STORE_NAME).clear();
 				}
 			},
 		});