## Summary - add an accessible, semantic-tone `Sparkline` primitive to `@chopin/visuals` - handle empty, single-point, constant, non-finite, and extreme finite series safely - add four-tone design-audit coverage and the shared semantic graphic role

## Scope Sparkline only. Mini bars, progress bars, tooltips, and product adoption remain separate slices.

## Verification - `bun test`: 1,485 pass, 2 PostgreSQL skips, 0 fail - `bun run types` - `bun run ci` - `bun run build` - `git diff --check`