refactor(playground)

[Fuyeors]

Summary

• rebuild the playground with Vue and the existing Vue renderer adapter
• add Markdown, Preview, JSON (AST), and HTML panes
• add the npm registry configuration from reference
• keep the layout free of a right sidebar and provide responsive mobile behavior

Validation

• vite build passes for packages/playground
• browser smoke test passes with no console output
• existing parser compatibility suite remains failing on pre-existing compatibility cases unrelated to this change