Use useTick instead of setInterval in devtools demo

[Chhavi001]

What changed

• Replaced setInterval with useTick in the devtools demo clock and counter.
• Did some small JSX formatting tweaks.

Why

• useTick is the recommended timer API in this library.
• Cleans up manual interval setup and cleanup.

Checklist

• npx tsc --noEmit passes
• npx vitest run passes
• New exports added to src/index.ts
• Documentation updated in docs/
  Note: 'npx vitest run' fails locally only on performance benchmark tests in src/tests/benchmarks.test.ts (time thresholds). Functional tests are passing.

[Chhavi001]

Hi! 👋

This PR replaces setInterval with useTick in the devtools demo clock and counter, to align with the recommended timer API. Please let me know if any changes are needed.

Thanks!

[hardy30894]

nit: trailing line in the end.

[Chhavi001]

Thanks for the review! I checked the file and it ends at line 159 with await app.waitUntilExit(); — there's no trailing line after that. Could you please point me to the exact location? Happy to fix it!