Add an `overflowTooltip` Svelte action that sets a native `title` only when
an element is actually clipped (ellipsis or line-clamp), re-checking on
resize. Native title is keyboard/touch reachable and zero-dep, unlike a
hover-only popover. Applied to the clipped titles on MangaCard, BookmarkList,
HistoryList, and the Continue-reading shelf.
Unit tests cover the overflow decision and the set/clear/update behaviour;
an e2e verifies a real-browser truncated card title gets the tooltip while a
short one does not.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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