Ports catalog.ts's tree renderer to components under
src/components/sidebar/, following docs/SIDEBAR.md: two-line cards
behind a 5px activity rail, adaptive meta line (duration, detail,
program, diff stat), collapsible folders, j/k walk, inline rename and a
right-click menu.
The nav walk reads a pure model (model.ts) rather than the DOM, so the
rule that an expanded folder header is skipped and a collapsed one is
not is testable without a render. Rail motion needs @keyframes, so it
stays in sidebar.css rather than the Tailwind config.
Closes#244
