fix(playground): render stored tracking state only in the browser

[sadjow]

After a reload with tracking disabled, the playground showed "DISABLED" styled green, as if tracking were on. The module's controls worked: enabling, disabling, capturing while disabled, and reloading all stored and skipped visits correctly. Only the playground's display was wrong.

The tracking preference and the history live in localStorage, which only the browser can read, so the server always renders the configured default: enabled, with no history. When the browser has a saved opt-out or stored entries, its first render disagrees with the server's HTML. Vue fixes mismatched text during hydration but keeps the server's class, and it warns that the class mismatch "will not be rectified in production".

The playground now wraps the status label and the collected data panel in <ClientOnly>, as the README recommends for displays of browser history. I drove the playground in Chromium through enabling, disabling, capturing while disabled, clearing, and reloading in each state. Before the change, the label kept the enabled class in five of eleven steps, and the console showed class and text hydration mismatches. After it, the class matched the text at every step and no hydration warnings appeared.

Validation: pnpm format:check, pnpm lint --max-warnings 0, pnpm test, and the playground type check pass.