> LLM call span tracking, prompt cache metrics, and Jaeger OTLP export

# Tracing & OpenTelemetry

Every model invocation, tool execution, and agent turn in Dewee generates structured OpenTelemetry-compatible traces (`internal/tracing/`).

## Tracing Architecture

* **Span Hierarchy:** `agent_run` → `model_turn` → `tool_execution` → `observation_capture`.
* **Prompt Cache Metrics:** Tracks cache read and cache creation tokens for Anthropic and OpenAI models.
* **Cost Rollups:** Calculates estimated token expenses per session and workspace.

## CLI Tracing Commands

```bash
# Follow real-time trace stream from the gateway
dewee traces follow

# List recent execution traces with error status
dewee traces list --status error

# Inspect full structured JSON span details
dewee traces get <trace-id>

# Export trace data for external ingestion
dewee traces export <trace-id>
```