The share button in the video modal was not being enabled correctly because `updateSourceAvailability` returned early if `sourceToggleContainer` was missing, skipping the `setShareEnabled` call.
This change ensures `setShareEnabled` is called based on `hasUrl` or `hasMagnet` before checking for `sourceToggleContainer`.
Added a regression test `tests/e2e/video-modal-share-bug.spec.ts`.