perf: optimize app startup and background lifecycles

electron/main/performance-diagnostics.ts

@@ -0,0 +1,53 @@
+import { app, BrowserWindow, webContents } from 'electron';
+import { monitorEventLoopDelay } from 'node:perf_hooks';
+
+export type PerformanceSnapshot = {
+  capturedAt: number;
+  eventLoopDelayMs: number;
+  gpu: ReturnType<typeof app.getGPUFeatureStatus>;
+  processes: Array<{
+    pid: number;
+    type: string;
+    cpuPercent: number;
+    workingSetSize: number;
+  }>;
+  windows: number;
+  webContents: number;
+  background: {
+    activity: { visible: boolean; module: string | null };
+    leaseCount: number;
+  };
+};
+
+type LifecycleDiagnostics = {
+  getActivity(): { visible: boolean; module: string | null };
+  getLeaseCount(): number;
+};
+
+// Keep the sampler alive for the process lifetime, but only expose aggregate
+// histogram values. No request payloads, URLs or project data enter this
+// diagnostic path.
+const eventLoopMonitor = monitorEventLoopDelay({ resolution: 20 });
+eventLoopMonitor.enable();
+
+export function collectPerformanceSnapshot(lifecycle?: LifecycleDiagnostics): PerformanceSnapshot {
+  const eventLoopDelayMs = eventLoopMonitor.max / 1e6;
+  eventLoopMonitor.reset();
+  return {
+    capturedAt: Date.now(),
+    eventLoopDelayMs: Math.round(eventLoopDelayMs * 100) / 100,
+    gpu: app.getGPUFeatureStatus(),
+    processes: app.getAppMetrics().map((metric) => ({
+      pid: metric.pid,
+      type: metric.type,
+      cpuPercent: metric.cpu.percentCPUUsage,
+      workingSetSize: metric.memory.workingSetSize,
+    })),
+    windows: BrowserWindow.getAllWindows().length,
+    webContents: webContents.getAllWebContents().length,
+    background: {
+      activity: lifecycle?.getActivity() ?? { visible: true, module: null },
+      leaseCount: lifecycle?.getLeaseCount() ?? 0,
+    },
+  };
+}