Editor: blockquote button is now a real toggle (turning it off works)
execCommand('formatBlock','blockquote') turns a quote ON but never turns
it OFF (browser quirk: the <blockquote> wrapper stays, even after ¶).
New toggleBlockquote() detects whether the caret is already inside a
blockquote and unwraps it (content put back in place, caret preserved);
otherwise it applies the quote. Button shows is-active when inside a quote.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@…>