test(runtime-fallback): fix OpenAI auto-retry test expectations

- Add timeout_seconds to mock config for auto-retry signal detection

- Add 'usage limit' pattern to quota_exceeded error classification

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>