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. -->

e2e-tests/snapshots/thinking_budget.spec.ts_thinking-budget-2.txt

@@ -8,14 +8,6 @@
         "role": "system",
         "content": "[[SYSTEM_MESSAGE]]"
       },
-      {
-        "role": "user",
-        "content": "tc=1"
-      },
-      {
-        "role": "assistant",
-        "content": "Error: Test case file not found: 1.md"
-      },
       {
         "role": "user",
         "content": "[dump] hi"