fix: preserve yarn releases when cleaning global cache

Previously rm -rf /root/.yarn deleted yarn binary itself. Now only
clean cache/telemetry/settings.yml files, keeping releases/ intact.

npm_install.py

@@ -2320,8 +2320,16 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
 
             shutil.rmtree(src_frontend / ".yarn", ignore_errors=True)
             shutil.rmtree(src_frontend / "node_modules", ignore_errors=True)
-            # Clean global Yarn 4.x cache with stale patch references
-            for g in [Path("/root/.yarn"), Path(os.path.expanduser("~/.config/yarn"))]:
+            # Clean global Yarn 4.x cache with stale patch references (keep yarn releases)
+            yarn_global = Path("/root/.yarn")
+            if yarn_global.exists():
+                for d in ["cache", "telemetry", "settings.yml", "yarnrc.yml"]:
+                    p = yarn_global / d
+                    if p.is_dir():
+                        shutil.rmtree(p, ignore_errors=True)
+                    elif p.is_file():
+                        p.unlink(missing_ok=True)
+            for g in [Path(os.path.expanduser("~/.config/yarn"))]:
                 if g.exists():
                     if g.is_dir():
                         shutil.rmtree(g, ignore_errors=True)