Summary

• Adds an OpenCode section to the README showing how to configure FreeLLMAPI as a custom provider
• Covers global and per-project config file locations
• Recommends auto as the default model so it works regardless of which providers are configured
• Includes a note that the model catalog changes and points readers to the Fallback Chain page / /v1/models for the live list

Test plan

• Docs-only change — no code modified, existing test suite passes (npm test: 143/143)