refactor: remove babel dependencies

- Remove babel dependencies as they're no longer needed
- Remove babel.config.cjs
- Update vite.config.ts comments
- JSX transpilation handled by esbuild in both dev and prod
- Verified Fast Refresh functionality

Co-Authored-By: [email protected] <[email protected]>

weave-js/src/contextProviders.tsx

@@ -55,7 +55,7 @@ export const ComputeGraphContextProviderFromClient: React.FC<{client: Client}> =
         data-test-num-shadow-server-requests-counter={
           GlobalCGEventTracker.shadowServerRequests
         }
-        className={isLoading ? 'loading cg-executing' : ''}
+        className={isLoading ? 'loading cg-executing test-fast-refresh' : ''}
         style={{height: '100%'}}>
         <ClientContext.Provider value={context}>
           {children}

weave-js/vite.config.ts

@@ -87,11 +87,7 @@ export default defineConfig(({mode, command}) => {
 
   // enable the react plugin in dev only, for fast refresh
 
-  // we're not using it in prod builds right now because it requires Babel,
-  // which is slow. To make sure the behavior is the same in both envs, we're
-  // NOT using the new JSX runtime in dev (so it should be equivalent to prod,
-  // where JSX transpilation is handled by esbuild, which doesn't support the
-  // new runtime yet)
+  // Using esbuild for JSX transpilation in both dev and prod
   if (mode !== 'production') {
     plugins.unshift(
       react({