Add OpenTelemetry trace export for TealEngine decisions

[nagasatish007]

Description

Integrate OpenTelemetry span export into TealEngine so every policy decision is traceable end-to-end.

Problem

TealEngine already generates correlation IDs compatible with OpenTelemetry trace format, but doesn't actually export spans. Teams using Jaeger, Datadog, or Grafana Tempo can't visualize the governance decision path.

Requirements

• Add optional @opentelemetry/api peer dependency
• Create spans for: policy evaluation start/end, each module evaluation, guardrail checks, cost calculation
• Attach decision metadata as span attributes (action, risk_score, reason_codes)
• Support both automatic instrumentation (if OTel SDK is initialized) and manual span injection
• Add a TealOTelPlugin that can be registered with TealEngineV12's module registry
• Export should be zero-cost when OTel is not configured (no-op tracer)

Technical Considerations

• Must not add @opentelemetry/api as a hard dependency (peer dep only)
• Use semantic conventions for span naming
• Consider span links for multi-agent correlation
• Baggage propagation for cross-service governance decisions

Validation

• Unit tests with mock tracer
• Example showing Jaeger integration
• Verify zero overhead when OTel is not initialized

Acceptance Criteria

• Spans exported for each governance decision
• Works with standard OTel collectors (Jaeger, OTLP)
• Zero runtime cost when OTel is not configured
• Documentation with setup example

[lleonardo-franco]

I'd like to work on this

[nagasatish007]

Assigned

[lleonardo-franco]

Implemented in agentguard-ai/tealtiger-typescript-prod#18. This adds optional OpenTelemetry tracing for engine decisions, module evaluation, guardrail checks, and cost calculation, with trace-link and baggage support plus Jaeger setup documentation.