OpenTelemetry in Ruby

Entry point for OpenTelemetry mechanics in Ruby applications. Load only the reference that matches the task; each reference is self-contained.

References

File	Use when
`references/setup.md`	Installing gems, configuring `OpenTelemetry::SDK.configure`, selecting OTLP exporters, setting resources and environment variables, and handling process shutdown.
`references/api.md`	Writing manual traces, metrics, or logs; managing context and propagation; testing emitted telemetry.
`references/instrumentation-libraries.md`	Selecting and configuring contrib instrumentation for Rails, Rack, Sinatra, HTTP clients, databases, jobs, messaging, and other gems.
`references/performance.md`	Tuning sampling, batching, cardinality, forked-process behavior, exporters, and lifecycle handling.
`references/breaking-changes.md`	Reviewing Ruby/runtime compatibility, independently versioned gems, experimental signal changes, and core/contrib upgrades.