feat: Add Amazon Nova as a model provider

[adhajar]

Description

Add support for Amazon Nova as a standalone model provider in opencode.

Requirements

• Add Nova as a provider with OpenAI-compatible API support
• Support NOVA_API_KEY environment variable for authentication
• Configure base URL to https://api.nova.amazon.com/v1
• Add nova-2-lite-v1 model with:
  • 64K context window
  • 10K max output tokens
  • Text and image input support
  • Tool calling capability
  • Reasoning support (low/medium/high effort levels)

Motivation

Nova provides powerful AI models that should be accessible through opencode's provider system.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• AWS Bedrock Claude models with Inference Profile ARNs fail to trigger Extended Thinking (Reasoning) #10611: AWS Bedrock Claude models reasoning configuration - mentions the current codebase has specific checks for handling Amazon Nova vs Claude/Anthropic models, which will be relevant to integrating Nova support

Feel free to ignore if this doesn't address your specific case.

[github-actions]

To stay organized issues are automatically closed after 90 days of no activity. If the issue is still relevant please open a new one.