fix: correct OTEL instrumentation wiring for agent traces

- Fix ActivitySource name from 'Microsoft.Agents.AI' to
  'Experimental.Microsoft.Agents.AI' matching the Agent Framework default
- Wrap agents with UseOpenTelemetry() via AIAgentBuilder so agent
  invocation spans are emitted to the configured OTLP collector
- Add proper disposal of OpenTelemetryAgent wrappers via
  SyncDisposableAdapter bridging IDisposable to IAsyncDisposable
- Enable workflow-level telemetry on WorkflowRunner custom graph builds
  via WithOpenTelemetry() (HandoffWorkflowBuilder and
  GroupChatWorkflowBuilder do not expose this API — framework limitation)
- Fix settings panel help text to be user-facing instead of dev jargon
- Update test assertion for corrected ActivitySource name

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/components/SettingsPanel.tsx

@@ -614,8 +614,8 @@ function TelemetrySection({
           placeholder={DEFAULT_OTEL_ENDPOINT}
         />
         <p className="mt-1.5 text-[11px] text-[var(--color-text-muted)]">
-          Use <span className="font-mono">bun run aspire</span> to launch the Aspire Dashboard locally at this default endpoint.
-          Changes take effect on the next sidecar session.
+          The URL of any OTLP-compatible collector (e.g. Jaeger, Aspire Dashboard, Grafana Alloy).
+          Changes take effect on the next session.
         </p>
       </div>
     </div>