Feature Request: Add Langfuse Tracing #219

Summary

Add tracing/observability to OpenCode using Langfuse.

Why

• Currently no way to trace execution or monitor performance
• Difficult to debug issues in production
• Missing insights on usage patterns and bottlenecks

Proposal

Integrate Langfuse (https://langfuse.com/) for tracing, which is already supported by Goose (https://block.github.io/goose/) per their documentation.

Benefits

• Simple debugging
• Performance monitoring
• Usage analytics
• Low implementation effort