Gaps in React wrapper

Two gaps in the wrapper at v0.2.0 that I had to work around:

1. picker-error is not surfaced as an on… prop. The underlying <drive-picker> element does dispatch picker-error CustomEvents — they're just not in DrivePickerEventHandlers. To preserve the iframe-side authorization-error signal, I attach a manual picker-error listener via a container ref + querySelector("drive-picker"). Worth filing upstream — onError should be a first-class prop alongside onPicked / onCanceled / onOauthError.

2. visible is not a prop. The wrapper renders <drive-picker> but doesn't forward a ref or expose visibility. Per the element's README, visible must be set imperatively on the DOM node. The same effect that wires the picker-error listener also sets element.visible = true. The dialog closes by flipping our local pickerOpen state on any of onPicked / onCanceled / onOauthError / picker-error, which unmounts the wrapper.

Start at the React wrapper's DrivePickerEventHandlers definition and wrapper entry point, then read the drive-picker element README for the visible property and event behavior. Confirm how onPicked, onCanceled, and onOauthError are exposed and how the wrapper renders the custom element. Done means picker-error is available through a first-class handler and visible can be controlled through the wrapper.