Make extension rewriting opt-in instead of opt-out

javascript/babel.config.cjs

@@ -23,7 +23,7 @@ module.exports = api => ({
     [
       '@babel/preset-typescript',
       {
-        rewriteImportExtensions: !api.env('test'),
+        rewriteImportExtensions: api.env('dist'),
       },
     ],
   ],

javascript/just.config.cjs

@@ -107,6 +107,10 @@ function babelTransformTask(opts) {
 
     return spawn(node, [require.resolve('@babel/cli/bin/babel'), ...args], {
       cwd: __dirname,
+      env: {
+        // Trigger distribution-specific Babel transforms
+        NODE_ENV: 'dist',
+      }
     });
   };
 }