refactor: replace runtime isElectron() with build-time isDesktop constant (#8710)

## Summary

Replace all runtime `isElectron()` function calls with the build-time
`isDesktop` constant from `@/platform/distribution/types`, enabling
dead-code elimination in non-desktop builds.

## Changes

- **What**: Migrate 30 files from runtime `isElectron()` detection
(checking `window.electronAPI`) to the compile-time `isDesktop` constant
(driven by `__DISTRIBUTION__` Vite define). Remove `isElectron` from
`envUtil.ts`. Update `isNativeWindow()` to use `isDesktop`. Guard
`electronAPI()` calls behind `isDesktop` checks in stores. Update 7 test
files to use `vi.hoisted` + getter mock pattern for per-test `isDesktop`
toggling. Add `DISTRIBUTION=desktop` to `dev:electron` script.

## Review Focus

- The `electronDownloadStore.ts` now guards the top-level
`electronAPI()` call behind `isDesktop` to prevent crashes on
non-desktop builds.
- Test mocking pattern uses `vi.hoisted` with a getter to allow per-test
toggling of the `isDesktop` value.
- Pre-existing issues not addressed: `as ElectronAPI` cast in
`envUtil.ts`, `:class="[]"` in `BaseViewTemplate.vue`,
`@ts-expect-error` in `ModelLibrarySidebarTab.vue`.
- This subsumes PR #8627 and renders PR #6122 and PR #7374 obsolete.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8710-refactor-replace-runtime-isElectron-with-build-time-isDesktop-constant-3006d73d365081c08037f0e61c2f6c77)
by [Unito](https://www.unito.io)

src/views/GraphView.vue

@@ -19,7 +19,7 @@
   <RerouteMigrationToast />
   <ModelImportProgressDialog />
   <ManagerProgressToast />
-  <UnloadWindowConfirmDialog v-if="!isElectron()" />
+  <UnloadWindowConfirmDialog v-if="!isDesktop" />
   <MenuHamburger />
 </template>
 
@@ -52,7 +52,7 @@ import { useProgressFavicon } from '@/composables/useProgressFavicon'
 import { SERVER_CONFIG_ITEMS } from '@/constants/serverConfig'
 import { i18n, loadLocale } from '@/i18n'
 import ModelImportProgressDialog from '@/platform/assets/components/ModelImportProgressDialog.vue'
-import { isCloud } from '@/platform/distribution/types'
+import { isCloud, isDesktop } from '@/platform/distribution/types'
 import { useSettingStore } from '@/platform/settings/settingStore'
 import { useTelemetry } from '@/platform/telemetry'
 import { useFrontendVersionMismatchWarning } from '@/platform/updates/common/useFrontendVersionMismatchWarning'
@@ -78,7 +78,7 @@ import { useServerConfigStore } from '@/stores/serverConfigStore'
 import { useBottomPanelStore } from '@/stores/workspace/bottomPanelStore'
 import { useColorPaletteStore } from '@/stores/workspace/colorPaletteStore'
 import { useSidebarTabStore } from '@/stores/workspace/sidebarTabStore'
-import { electronAPI, isElectron } from '@/utils/envUtil'
+import { electronAPI } from '@/utils/envUtil'
 import LinearView from '@/views/LinearView.vue'
 import ManagerProgressToast from '@/workbench/extensions/manager/components/ManagerProgressToast.vue'
 
@@ -111,7 +111,7 @@ watch(
       document.body.classList.add(DARK_THEME_CLASS)
     }
 
-    if (isElectron()) {
+    if (isDesktop) {
       electronAPI().changeTheme({
         color: 'rgba(0, 0, 0, 0)',
         symbolColor: newTheme.colors.comfy_base['input-text']
@@ -121,7 +121,7 @@ watch(
   { immediate: true }
 )
 
-if (isElectron()) {
+if (isDesktop) {
   watch(
     () => queueStore.tasks,
     (newTasks, oldTasks) => {

src/views/templates/BaseViewTemplate.vue

@@ -22,7 +22,8 @@
 <script setup lang="ts">
 import { nextTick, onMounted, ref } from 'vue'
 
-import { electronAPI, isElectron, isNativeWindow } from '@/utils/envUtil'
+import { electronAPI, isNativeWindow } from '@/utils/envUtil'
+import { isDesktop } from '@/platform/distribution/types'
 
 const { dark = false } = defineProps<{
   dark?: boolean
@@ -40,7 +41,7 @@ const lightTheme = {
 
 const topMenuRef = ref<HTMLDivElement | null>(null)
 onMounted(async () => {
-  if (isElectron()) {
+  if (isDesktop) {
     await nextTick()
 
     electronAPI().changeTheme({