Describe the bug

OpenAI provider does not use the ProviderRetry trait to retry completions.

To Reproduce

1. Use OpenAI provider
2. Receive a 429 or 503 from an OpenAI-compatible endpoint
3. The provider does not retry

Expected behavior
The provider should retry.

Please provide following information:

• OS & Arch: Fedora 42
• Interface: CLI
• Version: latest commit
• Provider & Model: OpenAI-compatible

Additional context
Looks like most/all of the other providers use the ProviderRetry trait to retry within the provider to force retries on failure, but the OpenAI provider does not.