feat(http-server): add OpenTelemetry tracing (Phase 1)

[Ignacio-Vidal]

Refs #2804

Summary

Adds OpenTelemetry (OTel) tracing to the Prism HTTP service (Phase 1 of #2804). Telemetry is opt-in via a configuration flag, and the OTLP/HTTP exporter endpoint is configurable, so users can point Prism at any remote OTel collector (Jaeger, Grafana Tempo, Datadog, an OpenTelemetry Collector, etc.).

When disabled (the default), Prism behaves exactly as before — the OTel SDK is never started and there is no overhead.

What's included

• New telemetry init module (packages/http-server/src/telemetry.ts): initTelemetry() wires up the OTel NodeSDK with an OTLP/HTTP trace exporter and HTTP auto-instrumentation. It is a no-op when disabled.
• The Micri request handler is wrapped in a server span when telemetry is enabled, recording request method, path, response status code, and exceptions on the error path.
• New CLI flags on both mock and proxy:
  • --telemetry (also via PRISM_TELEMETRY env var)
  • --otel-exporter-url (also via OTEL_EXPORTER_OTLP_ENDPOINT)
  • --otel-service-name (also via OTEL_SERVICE_NAME, defaults to prism)
  • CLI flags take precedence over env vars.
• Unit test for the telemetry module (enabled + disabled paths).
• End-to-end harness test asserting that enabling --telemetry does not change the served response.

Example usage

# Mock server with tracing to a local collector
prism mock api.oas.yaml \
  --telemetry \
  --otel-exporter-url http://localhost:4318/v1/traces \
  --otel-service-name prism-mock

# Proxy server, configured via standard OTel env vars
OTEL_EXPORTER_OTLP_ENDPOINT=http://collector:4318 \
OTEL_SERVICE_NAME=prism-proxy \
prism proxy api.oas.yaml https://upstream.example.com --telemetry

Checklist

• The basics
  • I tested these changes manually in my local or dev environment
• Tests
  • Added or updated
• Event Tracking
  • N/A
• Error Reporting
  • N/A

Additional context

• New runtime dependencies were added to packages/http-server/package.json (per CONTRIBUTING): @opentelemetry/sdk-node, @opentelemetry/api, @opentelemetry/exporter-trace-otlp-http, @opentelemetry/instrumentation-http, @opentelemetry/resources, @opentelemetry/semantic-conventions.
• Verified manually with the mock server (200/401/422 responses) and via the compiled binary that the OTel SDK bundles correctly and does not block startup when no collector is reachable.
• npm test passes (full suite). The new harness test passes; the only failing harness tests locally are the pre-existing proxy/* cases that require a reachable httpbin upstream.