feat(telemetry): add OpenTelemetry instrumentation with Aspire Dashboard support

[Hona]

Adds experimental OpenTelemetry support for debugging and observability.

What

• Full OTEL instrumentation: all tools, MCP, sessions, LLM, LSP, plugins
• Aspire Dashboard integration via bun run dev:otel
• Service differentiation: opencode-cli vs opencode-server
• Structured logs with full key=value context + exception stack traces
• AI SDK telemetry with GenAI message content capture

Enabling OpenTelemetry

1. Add to your global config (~/.config/opencode/opencode.json:

{
  "experimental": {
    "openTelemetry": true
  }
}

2. Run with Aspire Dashboard:

cd packages/opencode
bun run dev:otel

3. Open dashboard at http://localhost:18888

The OTEL_EXPORTER_OTLP_ENDPOINT env var controls the endpoint (defaults to http://localhost:4317).

Images