fix: [ENG-2885] address PR #699 review nits

- a11y: wrap smooth-scroll in @media (prefers-reduced-motion:
  no-preference) so users opted out of motion don't get the animation
  (WCAG 2.3.3).
- conflict-content-view: lift the marker-classification state out of
  the render-time .map() into a pure classifyMarkerLines() pre-pass.
  Render reads a precomputed boolean[]. Also reword the banner from
  "side-highlighted" to "marker lines highlighted" since only the
  three marker lines themselves carry the amber treatment today.
- topic-viewer-navigation: narrow onEntryClick param to {path: string}
  so the unused format/title fields no longer claim to be part of the
  contract. TopicViewer's IndexEntry stays assignable via width
  subtyping; test updated to match the narrower shape.
- markdown-view: import DEFAULT_WRAPPER_CLASS from conflict-content-
  view instead of duplicating the Tailwind string literal.