logging and presenting cpu/memory usage when app is force-closed (#1894)

closes #1803 











<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Detects when the app was force-closed and shows a dialog with the last
known CPU and memory usage. Adds background performance monitoring so we
can surface metrics on next launch.

- **New Features**
- Start a performance monitor at app launch; captures process and system
memory/CPU every 30s and on quit.
- Persist metrics in settings.lastKnownPerformance and track
settings.isRunning to detect improper shutdowns.
- On startup, if the previous run was force-closed, send a
"force-close-detected" IPC event after the window loads.
  - Add ForceCloseDialog to display timestamped process/system metrics.
- Whitelist the new IPC channel in preload and listen for it on the home
page.

<sup>Written for commit 0543cdc234da7f94024e8506749aaa9ca36ef916.
Summary will update automatically on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

src/lib/schemas.ts

@@ -257,6 +257,17 @@ export const UserSettingsSchema = z.object({
   releaseChannel: ReleaseChannelSchema,
   runtimeMode2: RuntimeMode2Schema.optional(),
   customNodePath: z.string().optional().nullable(),
+  isRunning: z.boolean().optional(),
+  lastKnownPerformance: z
+    .object({
+      timestamp: z.number(),
+      memoryUsageMB: z.number(),
+      cpuUsagePercent: z.number().optional(),
+      systemMemoryUsageMB: z.number().optional(),
+      systemMemoryTotalMB: z.number().optional(),
+      systemCpuPercent: z.number().optional(),
+    })
+    .optional(),
 
   ////////////////////////////////
   // E2E TESTING ONLY.