Add Poe (api.poe.com) as a provider plugin with OpenAI-compatible API.
- Create extensions/poe with plugin implementation
- Add API key validation via /v1/models endpoint
- Include 8 popular models: Claude, GPT-4o, Gemini, Llama
- Add unit tests (6 tests)
- Add documentation at docs/providers/poe.md
- Update provider index and docs navigation
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>