feat: add isNightly build flag for nightly-only features (#8149)

## Summary

Adds a compile-time `__IS_NIGHTLY__` constant that detects whether the
build is from the main branch (nightly) or a core/* branch (RC/stable).
The detection logic in vite.config.mts auto-detects based on
`GITHUB_REF_NAME === 'main'` in CI, with explicit override support via
`IS_NIGHTLY` environment variable. Exports `isNightly` from
`src/platform/distribution/types.ts` for use throughout the codebase.
Includes unit tests for the detection logic.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8149-feat-add-isNightly-build-flag-for-nightly-only-features-2ec6d73d365081c09930edec1c6644f5)
by [Unito](https://www.unito.io)

scripts/vite-define-shim.ts

@@ -12,6 +12,7 @@ declare global {
   const __ALGOLIA_API_KEY__: string
   const __USE_PROD_CONFIG__: boolean
   const __DISTRIBUTION__: 'desktop' | 'localhost' | 'cloud'
+  const __IS_NIGHTLY__: boolean
 }
 
 type GlobalWithDefines = typeof globalThis & {
@@ -22,6 +23,7 @@ type GlobalWithDefines = typeof globalThis & {
   __ALGOLIA_API_KEY__: string
   __USE_PROD_CONFIG__: boolean
   __DISTRIBUTION__: 'desktop' | 'localhost' | 'cloud'
+  __IS_NIGHTLY__: boolean
   window?: Record<string, unknown>
 }
 
@@ -36,6 +38,7 @@ globalWithDefines.__ALGOLIA_APP_ID__ = ''
 globalWithDefines.__ALGOLIA_API_KEY__ = ''
 globalWithDefines.__USE_PROD_CONFIG__ = false
 globalWithDefines.__DISTRIBUTION__ = 'localhost'
+globalWithDefines.__IS_NIGHTLY__ = false
 
 // Provide a minimal window shim for Node environment
 // This is needed for code that checks window existence during imports

src/platform/distribution/types.ts

@@ -9,6 +9,7 @@ type Distribution = 'desktop' | 'localhost' | 'cloud'
 
 declare global {
   const __DISTRIBUTION__: Distribution
+  const __IS_NIGHTLY__: boolean
 }
 
 /** Current distribution - replaced at compile time */
@@ -18,3 +19,10 @@ const DISTRIBUTION: Distribution = __DISTRIBUTION__
 export const isDesktop = DISTRIBUTION === 'desktop' || isElectron() // TODO: replace with build var
 export const isCloud = DISTRIBUTION === 'cloud'
 // export const isLocalhost = DISTRIBUTION === 'localhost' || (!isDesktop && !isCloud)
+
+/**
+ * Whether this is a nightly build (from main branch).
+ * Nightly builds may show experimental features and surveys.
+ * @public
+ */
+export const isNightly = __IS_NIGHTLY__

vite.config.mts

@@ -51,6 +51,14 @@ const DISTRIBUTION: 'desktop' | 'localhost' | 'cloud' =
       ? 'cloud'
       : 'localhost'
 
+// Nightly builds are from main branch; RC/stable builds are from core/* branches
+// Can be overridden via IS_NIGHTLY env var for testing
+const IS_NIGHTLY =
+  process.env.IS_NIGHTLY === 'true' ||
+  (process.env.IS_NIGHTLY !== 'false' &&
+    process.env.CI === 'true' &&
+    process.env.GITHUB_REF_NAME === 'main')
+
 // Disable Vue DevTools for production cloud distribution
 const DISABLE_VUE_PLUGINS =
   process.env.DISABLE_VUE_PLUGINS === 'true' ||
@@ -502,7 +510,8 @@ export default defineConfig({
     __ALGOLIA_APP_ID__: JSON.stringify(process.env.ALGOLIA_APP_ID || ''),
     __ALGOLIA_API_KEY__: JSON.stringify(process.env.ALGOLIA_API_KEY || ''),
     __USE_PROD_CONFIG__: process.env.USE_PROD_CONFIG === 'true',
-    __DISTRIBUTION__: JSON.stringify(DISTRIBUTION)
+    __DISTRIBUTION__: JSON.stringify(DISTRIBUTION),
+    __IS_NIGHTLY__: JSON.stringify(IS_NIGHTLY)
   },
 
   resolve: {

vitest.setup.ts

@@ -46,6 +46,7 @@ globalThis.__ALGOLIA_APP_ID__ = ''
 globalThis.__ALGOLIA_API_KEY__ = ''
 globalThis.__USE_PROD_CONFIG__ = false
 globalThis.__DISTRIBUTION__ = 'localhost'
+globalThis.__IS_NIGHTLY__ = false
 
 // Define runtime config for tests
 window.__CONFIG__ = {