- Set api: 'anthropic-messages' for claude-* models through LiteLLM
- Add LiteLLM to resolveCacheControlTtl for cache parameter passthrough
- Enables proper Anthropic cache control headers for cost savings
This fixes the missing cache support by ensuring:
1. Claude models use the correct API format (anthropic-messages)
2. Cache control TTL is resolved and passed through for LiteLLM
Add LiteLLM as a new OpenAI-compatible proxy provider:
- Add onboarding flow with API key, base URL, and model selection
- Fetch available models from LiteLLM /v1/models endpoint
- Auto-detect context window from /model/info endpoint
- Set supportsStore: false to avoid "Extra inputs are not permitted" errors
with providers that don't support the OpenAI Responses API store parameter
- Preserve compat settings through model resolution pipeline
- Add provider documentation
Closes#2639Closes#2305
Co-Authored-By: Claude <noreply@anthropic.com>
