[codex] Fix client auth timeout and expiry handling

[Flerpharos]

Summary

• fix loopback auth callback timeout handling so socket timeouts use remaining duration
• prevent Selenium browser cleanup failures from masking auth success or the original auth error
• reject explicit expired URL signing values instead of falling back to the default TTL

Fixes #198

Validation

• uv run --python 3.10 pytest --no-cov tests\test_client.py
• uv run --python 3.10 pre-commit run --all-files
• uv run --python 3.10 pre-commit run --all-files --hook-stage pre-push