feat: add OpenTelemetry settings UI and sidecar environment wiring

Add a global Telemetry section in the settings panel with:
- Toggle to enable/disable OTLP export
- Text input for the OTLP endpoint URL (default: http://localhost:4317)
- Guidance note about using \un run aspire\ for local testing

Wire the setting through the full stack:
- OpenTelemetrySettings type in shared domain with normalization
- IPC channel, preload binding, and handler for persistence
- SidecarClient forwards settings to createSidecarEnvironment
- Sidecar environment injects OTEL_EXPORTER_OTLP_ENDPOINT when enabled
- Settings loaded from workspace.json on startup and on change

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

tests/main/sidecarEnvironment.test.ts

@@ -37,4 +37,46 @@ describe('createSidecarEnvironment', () => {
       HTTPS_PROXY: 'http://proxy.local:8080',
     });
   });
+
+  test('injects OTEL_EXPORTER_OTLP_ENDPOINT when OpenTelemetry is enabled', () => {
+    expect(
+      createSidecarEnvironment(
+        { PATH: 'C:\\tools' },
+        { enabled: true, endpoint: 'http://localhost:4317' },
+      ),
+    ).toEqual({
+      PATH: 'C:\\tools',
+      OTEL_EXPORTER_OTLP_ENDPOINT: 'http://localhost:4317',
+    });
+  });
+
+  test('does not inject OTEL_EXPORTER_OTLP_ENDPOINT when OpenTelemetry is disabled', () => {
+    expect(
+      createSidecarEnvironment(
+        { PATH: 'C:\\tools' },
+        { enabled: false, endpoint: 'http://localhost:4317' },
+      ),
+    ).toEqual({
+      PATH: 'C:\\tools',
+    });
+  });
+
+  test('does not inject OTEL_EXPORTER_OTLP_ENDPOINT when settings are undefined', () => {
+    expect(
+      createSidecarEnvironment({ PATH: 'C:\\tools' }),
+    ).toEqual({
+      PATH: 'C:\\tools',
+    });
+  });
+
+  test('does not inject OTEL_EXPORTER_OTLP_ENDPOINT when endpoint is empty', () => {
+    expect(
+      createSidecarEnvironment(
+        { PATH: 'C:\\tools' },
+        { enabled: true, endpoint: '' },
+      ),
+    ).toEqual({
+      PATH: 'C:\\tools',
+    });
+  });
 });