fix: delete yarn binaries before corepack, check yarnpkg too

npm_install.py

@@ -2173,7 +2173,11 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
             # METHOD 1: Corepack (recommended for Yarn 4.x)
             if shutil.which("corepack"):
                 try:
-                    # Uninstall old yarn 1.x to prevent conflicts
+                    # Remove all yarn binaries to avoid conflicts
+                    subprocess.run(["rm", "-f", "/usr/local/bin/yarn", "/usr/local/bin/yarnpkg", "/usr/bin/yarn", "/usr/bin/yarnpkg"], check=False)
+                    subprocess.run(["rm", "-rf", "/usr/share/yarn"], check=False)
+                    
+                    # Uninstall old yarn 1.x
                     subprocess.run(["npm", "uninstall", "-g", "yarn"], check=False, cwd="/tmp")
                     
                     # Enable corepack
@@ -2203,7 +2207,11 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
                         )
                         
                         # Check version
-                        if shutil.which("yarn"):
+                        yarn_bin = shutil.which("yarn")
+                        yarnpkg_bin = shutil.which("yarnpkg")
+                        if DEBUG:
+                            print(f"   debug: which yarn={yarn_bin}, yarnpkg={yarnpkg_bin}")
+                        if yarn_bin:
                             major = _get_yarn_major_version(["yarn"])
                             
                             if major and major >= 4:
@@ -2211,6 +2219,14 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
                                     print(f"   ✓ Yarn {major}.x installed via corepack")
                                 os.chdir(original_cwd)
                                 return True
+                        
+                        if DEBUG:
+                            if yarnpkg_bin:
+                                major = _get_yarn_major_version(["yarnpkg"])
+                                if major and major >= 4:
+                                    print(f"   ✓ Yarn {major}.x installed via corepack (yarnpkg)")
+                                    os.chdir(original_cwd)
+                                    return True
                 except Exception as e:
                     if DEBUG:
                         print(f"   ⚠ Corepack method failed: {e}")