Vim refactor: migrate top-level News page to declarative nav (#104)

[binarypath]

Parent: #104

The /news page (separate from the News tab inside /security/{sym}) has its own category tabs row and a flat news-card list. Bespoke handler in vimHandlers.news.

Scope

• Category tab strip gets data-vim-row + per-tab data-vim-item.
• News cards get nested data-vim-row with single data-vim-item per card and data-vim-action="open-reader".
• Reader hijack already handled by the core dispatcher.

Acceptance

• h/l switches news categories.
• j/k navigates cards.
• Enter opens the reader.
• gg / G work.