fix(bundle): preserve root output path

Author: Lexiie

src/lib/bundle.test.ts

@@ -601,6 +601,10 @@ describe('resolveBundleDir', () => {
     const out = resolveBundleDir('/tmp/x/');
     expect(out).toBe('/tmp/x');
   });
+
+  it('preserves the filesystem root path', () => {
+    expect(resolveBundleDir('/')).toBe('/');
+  });
 });
 
 describe('streamUrlToFile retry', () => {

src/lib/bundle.ts

@@ -325,7 +325,7 @@ export function resolveBundleDir(rawPath: string): string {
       },
     });
   }
-  const trimmed = rawPath.endsWith('/') ? rawPath.slice(0, -1) : rawPath;
+  const trimmed = rawPath.endsWith('/') && rawPath.length > 1 ? rawPath.slice(0, -1) : rawPath;
   return isAbsolute(trimmed) ? trimmed : resolve(process.cwd(), trimmed);
 }