test(editor): address PR #147 review — reflow tests, code-block guard, a11y

Resolve the pre-merge review items for the #146 NodeView content-first fix:

- Export collectScrollAncestors/reflowAfterPaste and add editor-paste-handler
  unit tests covering ancestor selection (overlay included, non-overflowing
  auto excluded, X axis), the scrollHeight>clientHeight gate, scrollingElement
  dedup, the docEl==null branch, and the double-rAF nudge.
- Extend the structural guard with CodeBlockView and merge the two it.each
  blocks into one document-order assertion (handles the <pre> nesting where the
  contentDOM is not the literal first child).
- Simplify the post-paste nudge to a single scrollTo(scrollLeft, scrollTop).
- Document that the post-paste reflow runs on every paste path intentionally,
  and cross-reference the two #146 mitigations in both fixes.
- a11y: aria-hidden the decorative footnotes heading and number marker, and
  label the footnotes list via role="group" + aria-label so the visual reorder
  does not break screen-reader reading order (WCAG 1.3.2).
- CHANGELOG: add a Fixed entry noting the caret fix is macOS-verified manually.

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

apps/client/src/features/editor/components/code-block/code-block-view.tsx

@@ -53,7 +53,8 @@ export default function CodeBlockView(props: NodeViewProps) {
           menu is rendered after it and lifted back above visually via flex
           `order: -1` (the `.codeBlock` wrapper is a flex column — see
           code-block.module.css). It stays fully in flow as a full-width row
-          above the code: no overlay/absolute positioning. */}
+          above the code: no overlay/absolute positioning. The second #146
+          mitigation lives in editor-paste-handler.tsx (reflowAfterPaste). */}
       <pre
         spellCheck="false"
         hidden={