Options can now be written under a top-level extensions: key, as extensions: link-previews:. That is where editor tooling looks for them, so the new _schema.yml and _snippets.json give Quarto Wizard autocompletion, hover documentation, validation, and snippets for the five options. The bare top-level link-previews: block still works: keys from both places are combined, and the nested one wins a tie.
Fixes popover placement on a link that wraps across two lines. Such a link has one client rect per line and its bounding box is their union, which spans most of the text column, so hovering the tail of one line could open the preview a full column width away, too far to reach before the pointer left the link and the popover hid. It now anchors to the line box the pointer is in.
Adds a root example.qmd with the smallest working setup.