fix(vercel): bound command output and clean up running processes

[erulkey]

Commands can accumulate unread output in memory, and their local stream tasks can outlive sandbox termination. Stalled SDK responses can also exceed the requested command timeout.

Spool unread output to temporary files, enforce a local deadline, and cancel and join command tasks when the sandbox is terminated, including through a fresh handle or when lookup reports that it is already gone. Completed output remains readable after wait(), and long output lines are preserved. Consumed spool space is reclaimed when a reader catches up. This bounds queued-output memory at the cost of local disk I/O.

Both task teardown paths now close the providers they construct. Shared providers remain open; a close failure or timeout is logged without replacing the termination result.

Validation: 8,401 unit/protocol tests passed with 20 skips, including 155 focused provider and teardown tests. The package builds and installs from its wheel. The Labs example also exercises the provider in a live Vercel evaluation, including saved output and termination through a fresh handle. See the example validation scope.

This PR changes provider behavior and cleanup only. The standalone example and launcher stay in the Labs repository. No configuration changes are required.

Upstream CI is waiting for maintainer approval: CodeBuild reports “Pull request approval required for starting a build.” The build has not run yet.

Confidence Score: 5/5

The PR appears safe to merge; both previous findings are addressed and no new blocking issues were found.

Summary

The PR moves unread command output to temporary files, adds a local command deadline, and closes providers created for teardown.

The latest changes address both previous findings:

• Vercel command output stays readable without filling memory.
• Vercel commands stop when their requested timeout expires.
• Sandbox termination stops command tasks from every handle.
• Task teardown closes the providers it creates.

No new actionable issues were found. This review inspected code and tests; it did not run tests.

_{Reviews (2) · Last reviewed commit: "fix(vercel): finish missing-resource cle..." · Reviewed by Greptile}