OpenTelemetry in .NET

Entry point for OpenTelemetry mechanics in .NET services. Load a reference below based on the task; each reference is self-contained.

References

File	Use when
`references/setup.md`	Setting up the SDK via the DI/builder path (`AddOpenTelemetry().WithTracing/WithMetrics/WithLogging`, `UseOtlpExporter`, `OpenTelemetrySdk.Create`, `OpenTelemetry.Extensions.Hosting`), exporter wiring, env-var / `IConfiguration` inputs, and why there is no released declarative YAML config in .NET.
`references/api.md`	Instrumenting with native BCL APIs (`ActivitySource`/`Activity`, `System.Diagnostics.Metrics.Meter`, `ILogger`), how the SDK subscribes (`AddSource`/`AddMeter`), attributes, propagation, and the optional OTel API shim.
`references/instrumentation-libraries.md`	Zero-code (the `opentelemetry-dotnet-instrumentation` CLR-profiler agent), the contrib instrumentation-package catalog, and manual instrumentation following semconv.
`references/performance.md`	Tuning sampling, batch export processor, periodic metric reader, views, exporter choice, async context, graceful shutdown.
`references/breaking-changes.md`	Auditing existing code for deprecated/renamed APIs and semconv changes across recent core/contrib releases.