table/image/youtube bubble menus rendered permanently visible inline on load
(Tiptap v3 BubbleMenu positions in place and only reveals on node-selection,
unlike v2's tippy) — add a hidden-by-default in tiptap.css. Expand the tiptap
e2e to cover the interactive paths that let earlier bugs ship: menus-hidden-on-
load guard, bubble-menu-floats-on-select, mention popup end-to-end, toolbar cmd.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>