fix(app-router-playground): clean warnings and stabilize checks

[haddoumounir]

Summary

• fix async loading pages to run independent awaits in parallel
• replace unstable list keys and stale setState updates in playground components
• fix SVG JSX property casing for OG route output
• reduce LightSvg component size by extracting static markup constant
• remove rolldown client build warnings by stripping unsupported rollup keys in playground Vite config
• fix additional playground lint/type issues found during validation

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/vinext@694

commit: ef77913

[haddoumounir]

/bigbonk review