Add Amazon Nova as a provider with OpenAI-compatible chat completion API.
- Add Nova model definitions (Nova 2 Lite, Pro, Micro)
- Add --nova-api-key CLI flag for onboarding
- Add interactive and non-interactive auth handlers
- Add implicit provider resolution from NOVA_API_KEY env var
- Add Nova to auth choice options and preferred provider mapping
- Create docs/providers/nova.md documentation
Nova API endpoint: https://api.nova.amazon.com/v1
Default model: nova/nova-2-lite-v1
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
