## Why
Elevated sandbox tests share machine-local Windows accounts. Concurrent setup can rotate account passwords between another test's setup and logon.
## What changed
- Add a shared file-lock guard for elevated sandbox tests in `codex-core`, `codex-exec-server`, and `codex-windows-sandbox`, held through sandbox commands and cleanup.
- Queue these tests in a single-threaded Nextest group before their timeouts start, while retaining the file lock to coordinate other test processes.
- Limit account locking to tests that use elevated accounts and remove the sandbox crate's blanket Bazel `exclusive-if-local` tag.
GitOrigin-RevId: 26d4606cb1fdcac65926d29835bed4eac04c19c0
