Roll back persisted WSL config when start fails

Capture the previous on-disk WSL config before persisting the new one,
and restore it if startBackend fails. Otherwise the renderer error toast
leaves the UI showing the old toggle/distro while the disk has already
moved to the never-confirmed configuration, which the next app launch
silently honors.

Author: Jgratton24

apps/desktop/src/main.ts

@@ -1983,10 +1983,17 @@ function registerIpcHandlers(): void {
     if (distro !== null && !DISTRO_NAME_PATTERN.test(distro)) {
       return false;
     }
+    const previousConfig = loadWslConfig(STATE_DIR);
     saveWslConfig(STATE_DIR, { enabled: typed.enabled, distro });
     await stopBackendAndWaitForExit();
     const started = await startBackend();
     if (!started && typed.enabled) {
+      // Roll back so the on-disk config matches the renderer's view; the
+      // exponential-backoff restart will relaunch under the previous
+      // configuration. Without this, the renderer's error toast leaves the
+      // UI showing the old toggle while the next app launch silently honors
+      // the never-confirmed configuration.
+      saveWslConfig(STATE_DIR, previousConfig);
       throw new Error("Could not start the backend inside WSL.");
     }
     return true;