fix: support Firefox and Safari network error messages (#8949)

Fixes #8912

The `isNetworkError` check in `useErrorHandling.ts` only matched
Chrome/Edge's `"Failed to fetch"` message, causing Firefox and Safari
users to see raw error text instead of the user-friendly
`disconnectedFromBackend` toast.

Updated the check to use a case-insensitive regex matching all three
browser variants:
- Chrome/Edge: `Failed to fetch`
- Firefox: `NetworkError when attempting to fetch resource.`
- Safari: `Load failed`

Added parameterized tests covering all three browsers plus a negative
case ensuring non-`TypeError` errors are not misclassified.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8949-fix-support-Firefox-and-Safari-network-error-messages-30b6d73d36508185b2cbd6b5447d3795)
by [Unito](https://www.unito.io)

src/composables/useErrorHandling.test.ts

@@ -1,15 +1,18 @@
-import { createPinia, setActivePinia } from 'pinia'
+import { createTestingPinia } from '@pinia/testing'
+import { setActivePinia } from 'pinia'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import type { ErrorRecoveryStrategy } from '@/composables/useErrorHandling'
 import { useErrorHandling } from '@/composables/useErrorHandling'
+import { t } from '@/i18n'
+import { useToastStore } from '@/platform/updates/common/toastStore'
 
 describe('useErrorHandling', () => {
   let errorHandler: ReturnType<typeof useErrorHandling>
 
   beforeEach(() => {
     vi.clearAllMocks()
-    setActivePinia(createPinia())
+    setActivePinia(createTestingPinia())
     errorHandler = useErrorHandling()
   })
 
@@ -320,6 +323,45 @@ describe('useErrorHandling', () => {
       })
     })
 
+    describe('network error detection', () => {
+      it.each([
+        ['Failed to fetch', 'Chrome/Edge'],
+        ['NetworkError when attempting to fetch resource.', 'Firefox'],
+        ['Load failed', 'Safari']
+      ])('should show disconnected toast for "%s" (%s)', async (message) => {
+        const action = vi.fn(async () => {
+          throw new TypeError(message)
+        })
+
+        const wrapped = errorHandler.wrapWithErrorHandlingAsync(action)
+        await wrapped()
+
+        const toastStore = useToastStore()
+        expect(toastStore.add).toHaveBeenCalledWith(
+          expect.objectContaining({
+            severity: 'error',
+            detail: t('g.disconnectedFromBackend')
+          })
+        )
+      })
+
+      it('should not treat non-TypeError as network error', async () => {
+        const action = vi.fn(async () => {
+          throw new Error('Failed to fetch')
+        })
+
+        const wrapped = errorHandler.wrapWithErrorHandlingAsync(action)
+        await wrapped()
+
+        const toastStore = useToastStore()
+        expect(toastStore.add).toHaveBeenCalledWith(
+          expect.objectContaining({
+            detail: 'Failed to fetch'
+          })
+        )
+      })
+    })
+
     describe('backward compatibility', () => {
       it('should work without recovery strategies parameter', async () => {
         const action = vi.fn(async () => 'success')

src/composables/useErrorHandling.ts

@@ -53,7 +53,8 @@ export function useErrorHandling() {
   const toast = useToastStore()
   const toastErrorHandler = (error: unknown) => {
     const isNetworkError =
-      error instanceof TypeError && error.message === 'Failed to fetch'
+      error instanceof TypeError &&
+      /failed to fetch|networkerror|load failed/i.test(error.message)
     const message = isNetworkError
       ? t('g.disconnectedFromBackend')
       : error instanceof Error