Review Otel

Review the current code changes for OTel correctness and goobs pattern compliance.

Steps

1. Run git diff to see current changes (staged + unstaged)
2. For each changed file, verify:

Builder Pattern

• Constructor returns pointer to builder struct
• All chainable methods return *<Type> for fluency
• FromContext nil-checks ctx
• Attr(key string, val any) uses type switch with: string, int, int64, float64, bool, default

OTel Correctness

• Spans are always ended (defer span.End() or Done())
• Errors recorded on spans: span.RecordError(err) + span.SetStatus(codes.Error, ...)
• Metrics gated on Config.EnableMetrics and globalMeter != nil
• Instruments cached with mutex protection

Context Propagation