v3.4.0

Minor Changes

• 2c20134: Rust: optional otel feature that injects W3C trace context (traceparent) into
  every outbound request, so a call made through this client continues the caller's
  trace instead of starting a new root. Off by default — the crate does not link
  OpenTelemetry unless you ask for it. Guards an invalid span context and never
  overwrites a traceparent the caller set explicitly.

  TypeScript: the same injection at the same place — the single-request site, so every
  retry carries a current traceparent — behind an optional @opentelemetry/api peer
  dependency. Without it installed (or without a registered SDK) it is a no-op, not a
  crash, and no all-zero traceparent is ever emitted.

  Python: the same injection at the same place — the single-request site, so retries carry
  a current traceparent — behind an optional smooai-fetch[otel] extra. Without
  opentelemetry-api installed it is a no-op, not an import error.

  Go: the same injection at the same place — executeHTTPRequest, the single-request
  site inside the retry/timeout/breaker wrappers, so every attempt carries a current
  traceparent. Uses the OTel global propagator, which defaults to a no-op, so a
  service that never configured one sends nothing extra. Never overwrites a
  caller-set traceparent, and emits nothing at all when there is no valid span
  context.

  .NET: no change needed — HttpClient's DiagnosticsHandler already injects
  traceparent from the current Activity, ahead of redirects and connection
  pooling, and this client keeps that handler chain intact. Tests were added to pin
  that behaviour so a future custom primary handler cannot silently drop it.