Fix work item drawer expand crash on issue boards

What does this MR do and why?

Clicking the "Open in full page" (expand) button in the work-item drawer on an issue board crashed silently instead of navigating.

Root cause

The board issue card fragment (IssueNode) fetched webPath but never webUrl. The drawer's expand button navigates via activeItem.webUrl, so on issue boards webUrl was undefined and the click called visitUrl(undefined), throwing:

TypeError: Cannot read properties of undefined (reading 'startsWith')

The epic board fragment already requests webUrl, which is why epic boards were unaffected.

Fix

• Request webUrl in the issue fragment so it is cached on the active board item and available to the drawer.

Also included (unrelated cosmetic cleanup)

The disclosure-hierarchy ellipsis tooltip previously used a static, duplicated element ID and rendered even when the ellipsis button was absent, producing BootstrapVue "Unable to find target element by ID" console warnings on boards. It now uses a unique ID + ref-based target and only renders when the button exists. This clears the console warnings; it is not the cause of the crash above.

Related to #606339 (closed)