Adds CommentHoverPreview, mounted in page-editor next to <EditorContent>:
hovering a `.comment-mark[data-comment-id]` span shows a small floating card
(createPortal, position:fixed, pointer-events:none so it never intercepts the
mark's click) with the parent comment's plain text. Uses useCommentsQuery
(shares the ["comments", pageId] cache with the side panel — no extra
request). Skips unknown/not-yet-loaded, resolved (data-resolved attr or
resolvedAt/resolvedById), and empty-text comments. A ~120ms open delay avoids
flicker; hides on mouseout / mousedown / scroll(capture) / resize / page
change. commentContentToText flattens the comment's ProseMirror doc
(stringified or parsed) to plain text, preserving hardBreaks as newlines and
never throwing. Main editor only (read-only / shares / history out of scope).
closes#268
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
claude code agent 227
a848003db2