fix(daytona): isolate integration test cleanup (#702)

## Summary

Scopes Daytona integration-test cleanup to a single GitHub Actions run
and attempt, preventing concurrent CI runs from deleting each other’s
active sandboxes.

## Changes

- Add a per-execution sandbox label derived from GitHub’s run ID and
attempt, with a local-process fallback.
- Remove the ineffective pre-test cleanup, which cannot match sandboxes
from earlier runs once labels are per-execution.
- Configure a 15-minute Daytona auto-delete TTL after the existing
5-minute auto-stop interval, bounding leaks when a cancelled process
cannot run final cleanup.
- Correct the Deno reconnect integration test to keep its duration-based
sandbox active while opening a second client, because `close()`
terminates the remote deployment.