fix(transform): handle leading comments before use client/server directive

The preamble insertion regex only matched "use client"/"use server" at
the start of the file. Files with leading comments (e.g. biome-ignore
pragmas) before the directive caused the preamble to be prepended,
pushing the directive down and violating Next.js/Turbopack's requirement
that it be the first expression.

Widen the regex to skip leading line and block comments before matching
the directive.

Author: Narrator

packages/domscribe-transform/src/plugins/turbopack/turbopack.loader.spec.ts

@@ -462,6 +462,35 @@ describe('Turbopack Loader', () => {
       expect(directiveIndex).toBe(0);
     });
 
+    it('should inject preamble after use client with leading comments', async () => {
+      // Arrange — files with lint-ignore comments before "use client"
+      const source =
+        '/** biome-ignore-all */\n/** another comment */\n"use client";\nimport React from "react";';
+      const context = createLoaderContext('/test/InputGroup.tsx');
+      const asyncCallback = vi.fn();
+      context.async = vi.fn(() => asyncCallback);
+      mockInjector.inject.mockReturnValue(
+        createMockInjectorResult(
+          '/** biome-ignore-all */\n/** another comment */\n"use client";\ntransformed',
+          1,
+        ),
+      );
+
+      // Act
+      loaderModule.default.call(context, source);
+      await vi.waitFor(() => expect(asyncCallback).toHaveBeenCalled());
+
+      // Assert — comments + directive must come before the preamble
+      const outputCode = asyncCallback.mock.calls[0][1] as string;
+      const directiveIndex = outputCode.indexOf('"use client"');
+      const preambleIndex = outputCode.indexOf('__DOMSCRIBE_RELAY_PORT__');
+      expect(directiveIndex).toBeLessThan(preambleIndex);
+      // Comments should be preserved before the directive
+      expect(outputCode.indexOf('biome-ignore-all')).toBeLessThan(
+        directiveIndex,
+      );
+    });
+
     it('should inject client globals after use server directive', async () => {
       // Arrange
       const source = '"use server";\nexport async function action() {}';

packages/domscribe-transform/src/plugins/turbopack/turbopack.loader.ts

@@ -414,13 +414,14 @@ async function transformWithInit(
   if (preamble) {
     // Insert after 'use client'/'use server' directive so we don't
     // violate Next.js/Turbopack's requirement that it be the first expression.
+    // The regex allows leading comments (line or block) before the directive,
+    // which is valid JS and common in codebases using lint-ignore pragmas.
     const directiveMatch = transformedCode.match(
-      /^(['"])use (client|server)\1;?[ \t]*\r?\n?/,
+      /^(?:[ \t]*(?:\/\/[^\n]*|\/\*[\s\S]*?\*\/)[ \t]*\r?\n)*[ \t]*(['"])use (client|server)\1;?[ \t]*\r?\n?/,
     );
     if (directiveMatch) {
-      const directive = directiveMatch[0];
-      outputCode =
-        directive + preamble + transformedCode.slice(directive.length);
+      const prologue = directiveMatch[0];
+      outputCode = prologue + preamble + transformedCode.slice(prologue.length);
     } else {
       outputCode = preamble + transformedCode;
     }