[codex] Reject acquire after pool destroy

[aouxwoux]

Fixes #81.

What changed

• Reject acquire() immediately when the pool has already been destroyed.
• Keep the existing aborted error message used for aborted pending acquires.
• Preserve acquireFail event emission for the rejected acquire.
• Add a regression test that verifies the acquire does not wait for acquireTimeoutMillis and does not remain queued.

Verification

• npm run build
• npm test
• npm run lint