Telemetry event helpers.

The framework emits the standard Elixir :telemetry events so any host app can observe agent runs through the usual OTel / Telemetry.Metrics / LiveDashboard pipeline.

Events

• [:exagent, :run, :start] — measurements: %{system_time}, metadata: %{agent, prompt}
• [:exagent, :run, :stop] — measurements: %{duration}, metadata: %{agent, usage, steps}
• [:exagent, :run, :exception] — measurements: %{duration}, metadata: %{agent, reason}
• [:exagent, :tool, :stop] — measurements: %{duration}, metadata: %{tool_name, success}
• [:exagent, :model, :retry] — emitted by ExAgent.Models.Fallback before a retry or fallback; measurements: %{attempt, delay}, metadata: %{model, status, fallback}