Fix HTMLElement error event typings

[Copilot]

HTMLElement inherited Window-only error typings, so strict handlers for element load errors were rejected. Window.onerror remains special, but element error handlers should receive a single event object.

• DOM typings

  • Change shared GlobalEventHandlers.onerror to a single-argument UIEvent handler.
  • Use common Event for the shared "error" event map entry.
  • Narrow "error" to UIEvent on element/document event maps.
  • Redeclare Window-specific "error": ErrorEvent and onerror: OnErrorEventHandler.

• Regression coverage

  • Add compiler coverage for valid HTMLElement handlers and preserved Window behavior.

declare const el: HTMLElement;

el.onerror = (event: Event) => {};
el.addEventListener("error", (event: UIEvent) => {});

declare const win: Window;

win.onerror = (event, source, lineno, colno, error) => {};
win.addEventListener("error", (event: ErrorEvent) => {});

• Fixes HTMLElement inherits onerror and addListener("error" definitions that are unique to Window #62075