* chore(benchmarks): remove Vite 7 runner, update Next.js to 16.2.1
The vinext-rolldown benchmark runner was identical to the vinext runner
(both resolved to the same Vite version via catalog), producing
duplicate results on the dashboard. Remove it entirely and simplify
to a two-runner comparison: Next.js (Turbopack) vs vinext (Vite 8).
Also bump the Next.js benchmark dependency from 16.1.7 to 16.2.1 to
pick up recent performance improvements.
* fix: remove vinext-rolldown from pnpm-workspace.yaml, fix migration comment
Steve Faulkner