The "Load selected image" button

While the "Load selected image" button isn't ideal, it's the only guaranteed way to load an annotatable image. This is for several reasons:

• The Exhibit Builder doesn't trigger an event after applying an attachment. If it triggered an exhibit-builder-apply-attachment event after adding the attachment to the DOM, there wouldn't be the race condition that's preventing us from getting the new attachment's file ID.
• Even if the above event existed, Annotorious cannot make a hidden image annotatable. This means that every time the page loads or the user applies an attachment we'd need to open the "Annotate Image" drawer before loading the annotatable image. I don't think having a bunch of auto-opened fullsize images on the page is a good user experience.

Das Issue nennt keine Dateien oder Tests; beginne damit, den Button „Load selected image“ und den Attachment-Flow von Exhibit Builder nachzuverfolgen. Überprüfe die beschriebene Race Condition bei Events und die Einschränkung von Annotorious bei ausgeblendeten Bildern, und kläre das gewünschte Verhalten sowie die Akzeptanzkriterien, bevor du irgendetwas änderst.