Phoenix trace smoke test in CI

Scope

Add CI smoke test to verify OpenTelemetry tracing is working:

• Emit a synthetic span during CI pipeline
• Assert the span was received by Phoenix (Arize)
• Fail the job if zero spans received in last 2 minutes

Done When

• CI job added to .gitlab-ci.yml
• Synthetic span emitted in test
• Query Phoenix GraphQL API for span reception
• Job fails if no spans received
• Test passes on development branch

Context

Observability configuration:

• OTEL_EXPORTER_OTLP_ENDPOINT=http://192.168.139.2:4317
• TRACE_ENABLED=true
• Phoenix is running and accessible

Implementation Notes

Use GraphQL query to Phoenix to verify span reception:

query {
  traces(last: 10) {
    edges {
      node {
        traceId
        startTime
      }
    }
  }
}

Emit test span before query, then verify it appears in results.