fix(ci): add packageManager field for pnpm version specification

pnpm/action-setup requires either version input or packageManager field.

Author: ryota-murakami

package.json

@@ -63,5 +63,6 @@
       "esbuild",
       "unrs-resolver"
     ]
-  }
+  },
+  "packageManager": "pnpm@10.28.2"
 }