chore: Update with-solid example (#14895)
## Summary
- Refresh only `examples/with-solid` to exact registry-latest dependency
pins, including SolidStart 2.1.0, Solid 1.9.17, Vite 8.3.5, Vitest
5.0.5, ESLint 10.13.0, and Turborepo 2.11.10.
- Pin pnpm 12.15.0, raise the Node.js minimum to the current stable
release, 26.12.1, and regenerate the pnpm lockfile.
- Update the starter and app READMEs with example-specific scaffolding,
workspace-root installation, pnpm-filtered app commands, and local Turbo
remote-cache commands.
- Preserve the existing SolidStart v2 Vite/Nitro integration, ESLint
flat configuration, and Turbo task graph, which already match the
current toolchain. Leave release-age configuration unchanged.
Co-authored-by: vercel-gh-bot-4[bot] <312518292+vercel-gh-bot-4[bot]@users.noreply.github.com>