Proposal: Optional BoxLite sandbox backend (experimental)

[DorianZheng]

Summary

Could we add BoxLite as an optional sandbox backend?

This is not a replacement request. Existing runtime defaults can stay as-is.

Why

• Extra isolation option (micro-VM based).
• Good fit for projects that already have runtime abstraction.
• Opt-in only, so no disruption for existing users.

Tiny example (Node.js)

import { SimpleBox } from '@boxlite-ai/boxlite';

async function run(i: number) {
  const box = new SimpleBox({ image: 'alpine:latest', autoRemove: true });
  try {
    await box.exec('sh', '-lc', 'echo ok');
    const m = await box.metrics();
    console.log(`[box ${i}] totalCreateDurationMs=${m.totalCreateDurationMs}`);
  } finally {
    await box.stop();
  }
}

async function main() {
  await Promise.all([1, 2, 3].map(run));
}
main();

Warm startup is typically under 200ms.
Cold starts can be higher depending on image/cache state.

Suggested scope

1. Add optional boxlite backend.
2. Keep current runtime behavior unchanged unless explicitly selected.
3. Validate parity for mounts, timeout, and cleanup lifecycle.