Updated the DRAWER layout anchor selector to accept both the new testid (work-item-detail-panel-copy-button) and the old one (work-item-drawer-copy-button).

Updated the getUrl fallbacks in the ISSUE and STICKY HEADER layouts to look up the copy button via both testids.

Updated the doc comment for the DRAWER layout to mention the fallback.

Fix a bug where the "Copy as Markdown" button does not appear when a GitLab issue is marked as done.