feat(vercel-sandbox,sandbox): introduce keepLast parameters for SDK/CLI

[marc-vercel]

Re-apply #164, which was closed.

CLI

sandbox create accepts retention policy flags. By default, evicted snapshots are deleted immediately; pass --delete-evicted-snapshots false to let them fall back to the sandbox's default expiration instead.

> sandbox create --keep-last-snapshots 3
> sandbox create --keep-last-snapshots 3 --keep-last-snapshots-for 7d
> sandbox create --keep-last-snapshots 5 --keep-last-snapshots-for 30d --delete-evicted-snapshots false

The sandbox config command exposes one subcommand per retention field. The two modifier subcommands (keep-last-snapshots-for, delete-evicted-snapshots) require an existing policy.

> sandbox config keep-last-snapshots my-sandbox 3
> sandbox config keep-last-snapshots-for my-sandbox 7d
> sandbox config delete-evicted-snapshots my-sandbox false

# Pass 0 to remove the policy:
> sandbox config keep-last-snapshots my-sandbox 0

sandbox config list includes a new "Keep last snapshots" row:

> sandbox config list my-sandbox

FIELD                 VALUE
vCPUs                 2
Timeout               10 minutes
Persistent            true
Network policy        restricted
Snapshot expiration   7 days
Keep last snapshots   count=3, for=7 days, delete-evicted-snapshots=true
Current snapshot      -
Tags                  -

SDK

Sandbox.create and Sandbox.update accept a new optional keepLastSnapshots field.

const sandbox = await Sandbox.create({
  keepLastSnapshots: {
    count: 3,
    expiration: 7 * 24 * 60 * 60 * 1000,   // ms, 0 = never. Falls back to snapshotExpiration when omitted.
    deleteEvicted: true,                    // default true
  },
});

On Sandbox.update, pass null to remove the policy:

await sandbox.update({ keepLastSnapshots: null });

[vercel]

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Project	Deployment	Actions	Updated (UTC)
sandbox	Ready	Preview, Comment, Open in v0	May 15, 2026 9:14am
sandbox-cli	Ready	Preview, Comment, Open in v0	May 15, 2026 9:14am
sandbox-sdk	Ready	Preview, Comment, Open in v0	May 15, 2026 9:14am
sandbox-sdk-ai-example	Ready	Preview, Comment, Open in v0	May 15, 2026 9:14am
workflow-code-runner	Ready	Preview, Comment, Open in v0	May 15, 2026 9:14am