isTrusted was hardcoded to true for every Event, so new Event('x').isTrusted returned true. Real browsers return false for script-constructed events and true only for user-agent dispatched ones, so this was a trivial bot-detection tell (Closes#303).
Track trusted events in a closure-private WeakSet that page JS cannot read or forge; default isTrusted to false. The CDP input pipeline marks its synthesized mouse/key events trusted via a non-enumerable __obscura_markTrusted helper, so automation clicks stay trusted like real Chrome over CDP while page-built events report false.