cli: replace sandbox.kill() with setTimeout(1s) in create command to prevent snapshot deletions (#1256)

## Summary

In the CLI's `sandbox create` command, the `connectSandbox` function's
`finally` block previously called `sandbox.kill()` when the terminal
session ended. This replaces it with `sandbox.setTimeout(1_000)` so the
sandbox expires implicitly after 1 second rather than being explicitly
killed.

The motivation is that an explicit `kill()` can trigger deletion of
historic sandbox snapshots, whereas letting the sandbox time out avoids
that side effect.

### Updates since last revision

Addressed review feedback about a race condition: `clearInterval` stops
future keep-alive ticks but cannot cancel one already in-flight. The
keep-alive callback now stores its promise in a `pendingKeepAlive`
variable, and the `finally` block awaits it (with `.catch(() => {})`)
before setting the 1s shutdown timeout. This ensures an in-flight
`setTimeout(30_000)` cannot silently override the shutdown timeout.

## Review & Testing Checklist for Human

- [ ] **Verify that `sandbox.setTimeout(1_000)` does not trigger
snapshot deletion** — this is the core assumption behind the change.
Confirm that the implicit expiry path in the backend behaves differently
from the explicit `kill()` path with respect to snapshot preservation.
- [ ] **Test `e2b sandbox create` end-to-end**: connect a terminal,
exit, and confirm the sandbox is cleaned up within a few seconds and no
snapshots are lost.
- [ ] **Review the race condition fix**: confirm that `await
pendingKeepAlive.catch(() => {})` correctly serializes against the last
in-flight keep-alive before the 1s timeout is applied. Note that the
interval callback is no longer `async` — it just assigns the promise.
- [ ] **Edge case: what happens if `setTimeout` fails?** The sandbox
would remain alive with its previous 30s keep-alive timeout. Decide if
that's acceptable or if a fallback is needed.

### Notes
- The 1-second timeout value was chosen per the request. Adjust if a
different grace period is preferred.
- The keep-alive interval (`clearInterval`) is still stopped before
awaiting the pending promise, so no new ticks will fire.

Link to Devin session:
https://app.devin.ai/sessions/68081ba06fa54be9b8127ba1d68481ae

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: ben@e2b.dev <ben@e2b.dev>

Author: devin-ai-integration[bot]

.changeset/sandbox-timeout-instead-of-kill.md

@@ -0,0 +1,5 @@
+---
+'@e2b/cli': patch
+---
+
+Replace sandbox.kill() with sandbox.setTimeout(1s) in the CLI create command to prevent accidental historic sandbox snapshot deletions

packages/cli/src/commands/sandbox/create.ts

@@ -98,9 +98,10 @@ export async function connectSandbox({
   sandbox: e2b.Sandbox
   template: Pick<e2b.components['schemas']['Template'], 'templateID'>
 }) {
-  // keep-alive loop
-  const intervalId = setInterval(async () => {
-    await sandbox.setTimeout(30_000)
+  // keep-alive loop — track the in-flight promise so we can await it on shutdown
+  let pendingKeepAlive: Promise<void> = Promise.resolve()
+  const intervalId = setInterval(() => {
+    pendingKeepAlive = sandbox.setTimeout(30_000)
   }, 5_000)
 
   console.log(
@@ -112,7 +113,8 @@ export async function connectSandbox({
     await spawnConnectedTerminal(sandbox)
   } finally {
     clearInterval(intervalId)
-    await sandbox.kill()
+    await pendingKeepAlive.catch(() => {})
+    await sandbox.setTimeout(1_000)
     console.log(
       `Closing terminal connection to template ${asFormattedSandboxTemplate(
         template