fix(studio): guard import.meta.env for non-Vite consumers

manualEditingAvailability.ts unconditionally reads `import.meta.env`.
That's a Vite-only extension; in plain ESM hosts (Next.js / Turbopack,
Node, jest in some configs) `import.meta` exists but `import.meta.env`
is `undefined`. Reading any property off undefined throws at module
evaluation time, so the studio fails to load the moment a non-Vite
host imports anything from `@hyperframes/studio`.

Guard the read so the module is loadable everywhere; outside Vite,
every flag falls back to its declared default, preserving Vite
behavior.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: terencecho

packages/studio/src/components/editor/manualEditingAvailability.ts

@@ -27,7 +27,12 @@ export function resolveStudioBooleanEnvFlag(
   return fallback;
 }
 
-const env = import.meta.env as StudioFeatureFlagEnv;
+// `import.meta.env` is a Vite-only extension. In non-Vite ESM hosts
+// (Next.js / Turbopack, Node, jest in some configs) it's undefined,
+// and downstream `env[name]` reads would crash. Fall back to `{}` so
+// every flag resolves to its declared default outside Vite. Direct
+// property access keeps Vite's compile-time transform happy.
+const env = (import.meta.env ?? {}) as StudioFeatureFlagEnv;
 
 export const STUDIO_PREVIEW_MANUAL_EDITING_ENABLED = resolveStudioBooleanEnvFlag(
   env,