respect width/precision

ostd/format.hh

@@ -1042,7 +1042,10 @@ private:
             if constexpr(std::is_same_v<utf::unicode_base_t<C>, char>) {
                 range_put_all(writer, val.slice(0, n));
             } else {
-                while (!val.empty()) {
+                for (std::size_t i = 0; i < n; ++i) {
+                    if (val.empty()) {
+                        break;
+                    }
                     if (!utf::encode<char>(writer, val)) {
                         utf::replace<char>(writer);
                         val.pop_front();