feat: add role-specific statistics to telemetry and UI (cont. #15234) (#18824)

Co-authored-by: Yuna Seol <yunaseol@google.com>

packages/core/src/telemetry/uiTelemetry.test.ts

@@ -181,6 +181,7 @@ describe('UiTelemetryService', () => {
           thoughts: 2,
           tool: 3,
         },
+        roles: {},
       });
       expect(service.getLastPromptTokenCount()).toBe(0);
     });
@@ -236,6 +237,7 @@ describe('UiTelemetryService', () => {
           thoughts: 6,
           tool: 9,
         },
+        roles: {},
       });
       expect(service.getLastPromptTokenCount()).toBe(0);
     });
@@ -311,6 +313,7 @@ describe('UiTelemetryService', () => {
           thoughts: 0,
           tool: 0,
         },
+        roles: {},
       });
     });
 
@@ -356,6 +359,35 @@ describe('UiTelemetryService', () => {
           thoughts: 2,
           tool: 3,
         },
+        roles: {},
+      });
+    });
+
+    it('should update role metrics when processing an ApiErrorEvent with a role', () => {
+      const event = {
+        'event.name': EVENT_API_ERROR,
+        model: 'gemini-2.5-pro',
+        duration_ms: 300,
+        error: 'Something went wrong',
+        role: 'utility_tool',
+      } as unknown as ApiErrorEvent & { 'event.name': typeof EVENT_API_ERROR };
+
+      service.addEvent(event);
+
+      const metrics = service.getMetrics();
+      expect(metrics.models['gemini-2.5-pro'].roles['utility_tool']).toEqual({
+        totalRequests: 1,
+        totalErrors: 1,
+        totalLatencyMs: 300,
+        tokens: {
+          input: 0,
+          prompt: 0,
+          candidates: 0,
+          total: 0,
+          cached: 0,
+          thoughts: 0,
+          tool: 0,
+        },
       });
     });
   });